Energy storage system and alumina calcination applications

ABSTRACT

An energy storage system (TES) converts variable renewable electricity (VRE) to continuous heat at over 1000° C. Intermittent electrical energy heats a solid medium. Heat from the solid medium is delivered continuously on demand. Heat delivery via flowing gas establishes a thermocline which maintains high outlet temperature throughout discharge. The delivered heat which may be used for processes including power generation and cogeneration. In one application, the TES provides higher-temperature heat through non-combustible fluid to an alumina calcination system used to remove impurities or volatile substances and/or to incur thermal decomposition to a desired product.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 18/171,602, filed Feb. 20, 2023, which is adivisional of U.S. patent application Ser. No. 17/650,522, filed Feb. 9,2022¹. This application also claims priority under 35 USC § 120 to Ser.No. 18/142,564, filed on May 2, 2023, which is a continuation-in-part ofU.S. patent application Ser. No. 17/668,333, filed Feb. 9, 2022. Thisapplication also claims priority under 35 USC § 119(e) to:

-   U.S. Provisional Patent Application No. 63/459,540 filed on Apr. 14,    2023,-   U.S. Provisional Patent Application No. 63/338,805 filed on May 5,    2022,-   U.S. Provisional Patent Application No. 63/347,987 filed on Jun. 1,    2022,-   U.S. Provisional Patent Application No. 63/378,355 filed on Oct. 4,    2022,-   U.S. Provisional Patent Application No. 63/427,374 filed on Nov. 22,    2022, and-   U.S. Provisional Patent Application No. 63/434,919 filed on Dec.    22, 2022. ¹ . . . which is a continuation of PCT/US21/61041 under 35    USC § 120 and U.S. Pat. No. 11,603,776 under 35 USC § 120, granted    on Mar. 14, 2023 and filed Nov. 29, 2021, which claims benefit under    35 USC § 119(e) to U.S. Provisional Application No. 63/119,443,    filed on Nov. 30, 2020, U.S. Provisional Application No. 63/155,261,    filed on Mar. 1, 2021, U.S. Provisional Application No. 63/165,632,    filed on Mar. 24, 2021, U.S. Provisional Application No. 63/170,370,    filed on Apr. 2, 2021, and U.S. Provisional Application No.    63/231,155, filed on Aug. 9, 2021, as well as under 35 USC § 120 and    35 USC 365 to PCT/US2021/06141, filed Nov. 29, 2021.

The contents of these priority applications are incorporated byreference in their entirety and for all purposes.

BACKGROUND Technical Field

The present disclosure relates to thermal energy storage and utilizationsystems. More particularly, the present disclosure relates to an energystorage system that stores electrical energy in the form of thermalenergy, which can be used for the continuous supply of hot air, carbondioxide (CO₂), steam or other heated fluids, for various applicationsincluding the supply of heat for power generation. More specifically,the energy storage system provides higher-temperature heat to an aluminacalcination process in which a solid chemical compound is heated to acontrolled, high temperature in a controlled environment in the presenceof little to no oxygen to remove impurities or volatile substancesand/or to incur thermal decomposition to a desired product. As usedthroughout this disclosure, the terms calcination and activation mayrefer to dehydroxylation as well as other chemical changes driven byheat, including decomposition of calcium carbonate to calcium oxide andaluminum hydroxide to aluminum oxide.

Related Art

I. Thermal Energy Systems

A. Variable Renewable Electricity

The combustion of fossil fuels has been used as a heat source in thermalelectrical power generation to provide heat and steam for uses such asindustrial process heat. The use of fossil fuels has various problemsand disadvantages, however, including global warming and pollution.Accordingly, there is a need to switch from fossil fuels to clean andsustainable energy.

Variable renewable electricity (VRE) sources such as solar power andwind power have grown rapidly, as their costs have reduced as the worldmoves towards lower carbon emissions to mitigate climate change. But amajor challenge relating to the use of VRE is, as its name suggests, itsvariability. The variable and intermittent nature of wind and solarpower does not make these types of energy sources natural candidates tosupply the continuous energy demands of electrical grids, industrialprocesses, etc. Accordingly, there is an unmet need for storing VRE tobe able to efficiently and flexibly deliver energy at different times.

Moreover, the International Energy Agency has reported that the use ofenergy by industry comprises the largest portion of world energy use,and that three-quarters of industrial energy is used in the form ofheat, rather than electricity. Thus, there is an unmet need forlower-cost energy storage systems and technologies that utilize VRE toprovide industrial process energy, which may expand VRE and reducefossil fuel combustion.

B. Storage of Energy as Heat

Thermal energy in industrial, commercial, and residential applicationsmay be collected during one time period, stored in a storage device, andreleased for the intended use during another period. Examples includethe storage of energy as sensible heat in tanks of liquid, includingwater, oils, and molten salts; sensible heat in solid media, includingrock, sand, concrete and refractory materials; latent heat in the changeof phase between gaseous, liquid, and solid phases of metals, waxes,salts and water; and thermochemical heat in reversible chemicalreactions which may absorb and release heat across many repeated cycles;and media that may combine these effects, such as phase-changingmaterials embedded or integrated with materials which store energy assensible heat. Thermal energy may be stored in bulk underground, in theform of temperature or phase changes of subsurface materials, incontained media such as liquids or particulate solids, or inself-supporting solid materials.

Electrical energy storage devices such as batteries typically transferenergy mediated by a flowing electrical current. Some thermal energystorage devices similarly transfer energy into and out of storage usinga single heat transfer approach, such as convective transfer via aflowing liquid or gas heat transfer medium. Such devices use“refractory” materials, which are resistant to high temperatures, astheir energy storage media. These materials may be arranged inconfigurations that allow the passage of air and combustion gasesthrough large amounts of material.

Some thermal energy systems may, at their system boundary, absorb energyin one form, such as incoming solar radiation or incoming electricpower, and deliver output energy in a different form, such as heat beingcarried by a liquid or gas. But thermal energy storage systems must alsobe able to deliver storage economically. For sensible heat storage, therange of temperatures across which the bulk storage material—the“storage medium”—can be heated and cooled is an important determinant ofthe amount of energy that can be stored per unit of material. Thermalstorage materials are limited in their usable temperatures by factorssuch as freezing, boiling, or thermally driven decomposition ordeterioration, including chemical and mechanical effects.

Further, different uses of thermal energy—different heating processes orindustrial processes—require energy at different temperatures.Electrical energy storage devices, for example, can store and returnelectrical energy at any convenient voltage and efficiently convert thatvoltage up or down with active devices. On the other hand, theconversion of lower-temperature heat to higher temperatures isintrinsically costly and inefficient. Accordingly, a challenge inthermal energy storage devices is the cost-effective delivery of thermalenergy with heat content and at a temperature sufficient to meet a givenapplication.

Some thermal energy storage systems store heat in a liquid that flowsfrom a “cold tank” through a heat exchange device to a “hot tank” duringcharging, and then from the hot tank to the cold tank during discharge,delivering relatively isothermal conditions at the system outlet duringdischarge. Systems and methods to maintain sufficient outlet temperaturewhile using lower-cost solid media are needed.

Thermal energy storage systems generally have costs that are primarilyrelated to their total energy storage capacity (how many MWh of energyare contained within the system) and to their energy transfer rates (theMW of instantaneous power flowing into or out of the energy storage unitat any given moment). Within an energy storage unit, energy istransferred from an inlet into storage media, and then transferred atanother time from storage media to an outlet. The rate of heat transferinto and out of storage media is limited by factors including the heatconductivity and capacity of the media, the surface area across whichheat is transferring, and the temperature difference across that surfacearea. High rates of charging are enabled by high temperature differencesbetween the heat source and the storage medium, high surface areas, andstorage media with high heat capacity and/or high thermal conductivity.

Each of these factors can add significant cost to an energy storagedevice. For example, larger heat exchange surfaces commonly require 1)larger volumes of heat transfer fluids, and 2) larger surface areas inheat exchangers, both of which are often costly. Higher temperaturedifferences require heat sources operating at relatively highertemperatures, which may cause efficiency losses (e.g. radiation orconductive cooling to the environment, or lower coefficient ofperformance in heat pumps) and cost increases (such as the selection anduse of materials that are durable at higher temperatures). Media withhigher thermal conductivity and heat capacity may also require selectionof costly higher-performance materials or aggregates.

Another challenge of systems storing energy from VRE sources relates torates of charging. A VRE source, on a given day, may provide only asmall percentage of its full capacity, due to prevailing conditions. Foran energy storage system that is coupled to a VRE source and that isdesigned to deliver continuous output, all the delivered energy must beabsorbed during the period when incoming VRE is available. As a result,the peak charging rate may be some multiple of the discharge rates(e.g., 3-5×), for instance, in the case of a solar energy system, if thedischarge period (overnight) is significantly longer than the chargeperiod (during daylight). In this respect, the challenge of VRE storageis different from, for example, that of heat recuperation devices, whichtypically absorb and release heat at similar rates. For VRE storagesystems, the design of units that can effectively charge at high ratesis important, and may be a higher determinant of total system cost thanthe discharge rate.

C. Thermal Energy Storage Problems and Disadvantages

The above-described approaches have various problems and disadvantages.Earlier systems do not take into account several critical phenomena inthe design, construction, and operation of thermal energy storagesystems, and thus does not facilitate such systems being built andefficiently operated. More specifically, current designs fail to address“thermal runaway” and element failure due to non-uniformities in thermalenergy charging and discharging across an array of solid materials,including the design of charging, discharging, and unit controls toattain and restore balances in temperature across large arrays ofthermal storage material.

Thermal energy storage systems with embedded radiative charging andconvective discharging are in principle vulnerable to “thermal runaway”or “heat runaway” effects. The phenomenon may arise from imbalances,even small imbalances, in local heating by heating elements and incooling by heat transfer fluid flow. The variations in heating rate andcooling rate, unless managed and mitigated, may lead to runawaytemperatures that cause failures of heaters and/or deterioration ofrefractory materials. Overheating causes early failures of heatingelements and shortened system life. In Stack, for example, the bricksclosest to the heating wire are heated more than the bricks that arefurther away from the heating wire. As a result, the failure rate forthe wire is likely to be increased, reducing heater lifetime.

One effect that further exacerbates thermal runaway is the thermalexpansion of air flowing in the air conduits. Hotter air expands more,causing a higher outlet velocity for a given inlet flow, and thus ahigher hydraulic pressure drop across the conduit, which may contributeto a further reduction of flow and reduced cooling during discharge.Thus, in successive heating and cooling cycles, progressively less localcooling can occur, resulting in still greater local overheating.

The effective operation of heat supply from thermal energy storagerelies upon continuous discharge, which is a particular challenge insystems that rely upon VRE sources to charge the system. Solutions areneeded that can capture and store that VRE energy in an efficient mannerand provide the stored energy as required to a variety of uses,including a range of industrial applications, reliably and withoutinterruption.

Previous systems do not adequately address problems associated with VREenergy sources, including variations arising from challenging weatherpatterns such as storms, and longer-term supply variations arising fromseasonal variations in VRE generation. In this regard, there is an unmetneed in the art to provide efficient control of energy storage systemcharging and discharging in smart storage management. Current designs donot adequately provide storage management that considers a variety offactors, including medium-term through short-term weather forecasts, VREgeneration forecasts, and time-varying demand for energy, which may bedetermined in whole or in part by considerations such as industrialprocess demand, grid energy demand, real-time electricity prices,wholesale electricity market capacity prices, utility resource adequacyvalue, and carbon intensity of displaced energy supplies. A system isneeded that can provide stored energy to various demands thatprioritizes by taking into these factors, maximizing practical utilityand economic efficiencies.

There are a variety of unmet needs relating generally to energy, andmore specifically, to thermal energy. Generally, there is a need toswitch from fossil fuels to clean and sustainable energy. There is alsoa need to store VRE to deliver energy at different times in order tohelp meet society's energy needs. There is also a need for lower-costenergy storage systems and technologies that allow VRE to provide energyfor industrial processes, which may expand the use of VRE and thusreduce fossil fuel combustion. There is also a need to maintainsufficient outlet temperature while using lower-cost solid media.

Still further, there is a need to design VRE units that can be rapidlycharged at low cost, supply dispatchable, continuous energy as requiredby various industrial applications despite variations in VRE supply, andthat facilitate efficient control of charging and discharging of theenergy storage system.

II. Alumina Calcination Applications

A. Calcination Concepts and Methods

The term “calcination” broadly refers to a process in which a solidchemical compound is heated to a controlled, high temperature in acontrolled environment in the presence of little to no oxygen to removeimpurities and/or to incur thermal decomposition to a desired product.Calcination has traditionally referred to a process for decomposinglimestone (or calcium carbonate) into quicklime (calcium oxide) andcarbon dioxide. This reaction is widely used in industry given thatlimestone is an abundant mineral and that quicklime is used in theproduction of cement, mortar, plaster, paint, steel, paper and pulp aswell as in the treatment of water and flue gases.

Other calcination processes include the dehydroxylation (i.e., removalof crystalline water) of gypsum used in producing building materials andother products, dehydroxylation of alumina used in producing aluminummetal and other products, and dehydroxylation of clay minerals, whichmay be used for the activation of clay for use as a supplementarycementitious material (SCM) in a cement mixture, such as alongsidePortland cement. Clay mineral activation differs from its limestonecounterpart in that the reaction releases water (—OH groups) instead ofCO₂.

Different calcination reactions require different operating conditions(e.g., temperature, environment compositions, etc.) to expose mineralsto heat and drive calcination. Over time, different designs have beendeveloped, including shaft furnaces, rotary kilns, multiple hearthfurnaces, and fluidized bed reactors. Many associated processes havealso been developed including internal radiant heating via fuelcombustion within a kiln or reactor, internal convective heating via hotgas flow within a kiln or reactor, or external heating of a kiln orreactor. These traditional modes are referred to as soak-calcinationprocesses, given that the material takes several minutes to hours in thereaction chamber to become fully activated.

Flash calcination is another approach, which is more rapid than the soakprocess, and takes place in a reactor that uses gases at velocities andtemperatures creating gas-particle interactions including entrainmentand suspension, so as to drive effective heat transfer and encouragechemical reactions. Systems using this principle commonly introduce agas that has been heated via combustion of a fuel (including directexhausted combustion products) and/or a gas that may be heated fromcooling the products of calcination (or recovered from other heatsources, at the bottom of a reaction chamber in an up-flowconfiguration). The gas temperature may commonly range from 600° C. to1100° C. In one implementation, raw clay material to be processed isfinely divided and is fed into a chamber above the hot gas injectionpoint. Upward flowing hot gases interact with raw material and maysuspend the raw material through the chamber where the particles arequickly heated by the flowing gases.

Additional sources of heat may be incorporated within (or without) thechamber, including fuel combustion devices or additional hot gasintroduction ports, to maintain a desired temperature profile or ambientgas composition. As the material exits the chamber, it has been heatedto the desired state of calcination (or activation). The gas compositionwithin the chamber may be selected to perform a function of controllingthe quality of the product. For example, oxygen may be excluded or theremay be a reducing atmosphere zone for quality control of the product.The material to be processed may contain iron that will become oxidizedin non-reducing environments and cause the product to change color whichmay not be desired. This atmosphere reduction zone may be enforced viainjection of reducing gases or supplied via supplemental burners inwhich any oxygen in the air is reduced via injected fuel. After heatingand calcination, the material is then rapidly cooled, often by air incooling cyclones or another form of air quench. Water can also be usedas a cooling fluid in certain processes. The product is cooled to atemperature below 100° C.

Some attempts have been made to analyze clay calcination in gassuspension heaters in order to determine the effect of operatingconditions. In one example, a kaolinite particle feed was added above aburner and passed through the chamber with and without supplementalburners along the channel. Convection was the dominant form of heattransfer in the process where an ideal gas supply temperature was about900° C., e.g., 900° C., without supplemental burners.

With respect to the calciner stage, art approaches perform aluminacalcination in two stages: a first stage at a lower temperatureassociated with a decomposer and steam separation to perform partialcalcination, and a second stage at a higher temperature than the firststage, but at a lower temperature than would be required if calcinationwas performed in a single stage. The first stage may be at a temperaturesuch as 350° C., and the second stage may be in the range of 750° C. to950° C. The two-stage calcination process provides energy efficiencyadvantages over a single stage calcination process. Similar to claycalcination, a fuel is provided as an input to the first calcinationstage and the second calcination stage. The heat that is output fromcalcination may be provided for reading and waste heat recovery, withthe remaining heat being expelled after water cooling via stack gasoutput.

In these approaches, internal electrical resistive heaters cannotcost-effectively directly replace a burner in the calciner, for tworeasons. Heating the large gas volume needed for gas suspension purelyvia resistive heaters with known resistive heaters requires large spaceand cost. Additionally, known resistive heaters may experiencedegradation due to the particulate matter present in a calcinationprocess interacting with and degrading the heater surfaces.

B. Conventional Heating Sources

A calciner is a high-temperature furnace that is used to heat materialsto very high temperatures, typically above 800° C. The heating sourcesused in calciners can vary depending on the specific design andapplication. The choice of heating source for a calciner will depend ona number of factors, including the specific application, the size of thefurnace, and the availability and cost of the heating source.

Natural gas is a commonly used fuel in calciners because it is readilyavailable, efficient, and produces a high heat output. It is often usedin combination with a forced-air burner, which blows hot air into thefurnace to achieve the desired temperature. Similarly, propane isanother commonly used fuel in calciners because it is also readilyavailable and produces a high heat output. Like natural gas, it is oftenused in combination with a forced-air burner to achieve the desiredtemperature.

Fuel oil is another option for heating a calciner, although it is lesscommonly used than natural gas or propane. It is often used incombination with a combustion chamber that burns the fuel to produce hotgases that are then used to heat the furnace. Coal can be used as aheating source in a calciner, although it is less commonly used thannatural gas or propane. It is often used in combination with acombustion chamber that burns the coal to produce hot gases that arethen used to heat the furnace.

C. Conventional Calcination Processes—Problems and Disadvantages

Conventional calcination processes are used in various industries tobring about a chemical or physical change in a material by heating it toa high temperature. However, these processes have several problems anddisadvantages. The first issue is the high energy consumption requiredfor these processes, which can lead to high operating costs andenvironmental concerns. The second disadvantage is the time-consumingnature of calcination processes, especially for materials that requirehigh temperatures for a prolonged period. This can limit productioncapacity and increase costs.

Conventional alumina calcination involves heating the cooled, wetgibbsite to 950° C.-1100° C. to remove free and crystalline moisture inthe gibbsite, which is derived from bauxite. Art approaches have used arotary kiln or calciner using heat from combustion. According to someart approaches, the material first enters a high-pressure calcinationstep (e.g., the decomposer), for example at 6-8 bar and 300° C.-480° C.,and removes all the free moisture (e.g., drying) and activates asignificant portion of the gibbsite to alumina. These mechanisms producewater vapor as effluent. The partially calcined material passes througha pressure reducer to the lower pressure calcination stage. This occursat ambient pressure and relatively lower temperatures of 850° C.-950° C.Fuel and air that is preheated in the cooling of the product material iscombusted in a gas suspension calciner. The heat from the flue gas isfurther recovered by being passed into a steam generator/superheaterwhere is exchanges heat with recycled steam from the first stage,recycled steam from other steps in the Bayer process, or makeup water tosupply the first calcination step (or decomposer) with superheatedsteam.

These approaches may have problems and disadvantages. For example, whensteam is used as a heat transfer medium in calcination stage, it isnecessary to account for the plant balance, as the high mass flow ofsuperheated high-pressure steam must be filtered and cleaned beforerecirculating to other areas of the plant. The theoretically morefavorable heat balance from collecting high temperature moisture fromthe decomposer also translates to a more complex, integrated process.The large mass flow leads to art problems in supplying the correctquantity of superheated steam. The steam generator/superheater is amajor area for concern, both from the thermodynamic and operatingstandpoint. Additional fuel must be fired in this step. Additionally,buildup of contaminants or other degradation in process equipment is oneof the largest issues in the concept, as the recirculated steam oftenmust be cleaned and filtered of particulate matter before interactingwith the steam generator and superheater.

Another problem with conventional calcination processes is the limitedcontrol over temperature and atmosphere inside the furnace, which canaffect the final product quality. Additionally, during calcination,unwanted byproducts such as carbon dioxide and other gases can beformed, leading to environmental pollution and health hazards.Furthermore, conventional calcination processes may not be suitable forall types of materials, such as those that are sensitive to hightemperatures or those that require a specific atmosphere duringprocessing. Lastly, high-temperature calcination can cause significantwear and tear on furnace equipment, requiring frequent maintenance andrepair. To overcome these disadvantages, alternative calcinationprocesses such as microwave calcination, flash calcination, and sol-gelcalcination have been developed. These processes offer advantages suchas lower energy consumption, faster processing times, better controlover temperature and atmosphere, and reduced formation of unwantedbyproducts.

SUMMARY

The example implementations advance the art of thermal energy storageand enable the practical construction and operation of high-temperaturethermal energy storage systems which are charged by VRE, store energy insolid media, and deliver high-temperature heat.

I. Thermal Energy Storage System

This Section I of the Summary relates to the disclosure as it appears inU.S. patent application Ser. No. 18/171,602, of which this applicationis a continuation-in-part.

Aspects of the example implementations relate to a system for thermalenergy storage, including an input, (e.g., electricity from a variablerenewable electricity (VRE) source), a container having sides, a roofand a lower platform, a plurality of vertically oriented thermal storageunits (TSUs), inside the container, the TSUs each including a pluralityof stacks of bricks and heaters attached thereto, each of the heatersbeing connected to the input electricity via switching circuitry, aninsulative layer interposed between the plurality of TSUs, the roof andat least one of the sides, a duct formed between the insulative layerand a boundary formed by the sides, an inner side of the roof and thelower platform of the container, a blower that blows relatively coolerfluid such as air or another gas (e.g. CO₂) along the flow path, anoutput (e.g., hot air at prescribed temperature to industrialapplication), a controller that controls and co-manages the energyreceived from the input and the hot air generated at the output based ona forecast associated with an ambient condition (e.g., season orweather) or a condition (e.g., output temperature, energy curve, etc.).The exterior and interior shapes of the container may be rectangular,cylindrical (in which case “sides” refers to the cylinder walls), orother shapes suitable to individual applications.

The terms air, fluid and gas are used interchangeably herein to refer toa fluid heat transfer medium of any suitable type, including varioustypes of gases (air, CO₂, oxygen and other gases, alone or incombination), and when one is mentioned it should be understood that theothers can equally well be used. Thus, for example, “air” can be anysuitable fluid or gas or combinations of fluids or gases.

Thermal energy storage (TES) systems according to the present designscan advantageously be integrated with or coupled to steam generators,including heat recovery steam generators (HRSGs) and once-through steamgenerators (OTSGs). The terms “steam generator”, “HRSG”, and “OTSG” areused interchangeably herein to refer to a heat exchanger that transfersheat from a first fluid into a second fluid, where the first fluid maybe air circulating from the TSU and the second fluid may be water (beingheated and/or boiled), oil, salt, air, CO₂, or another fluid. In suchimplementations, the heated first fluid is discharged from a TES unitand provided as input to the steam generator, which extracts heat fromthe discharged fluid to heat a second fluid, including producing steam,which heated second fluid may be used for any of a variety of purposes(e.g. to drive a turbine to produce shaft work or electricity). Afterpassing through a turbine, the second fluid still contains significantheat energy, which can be used for other processes. Thus, the TES systemmay drive a cogeneration process. The first fluid, upon exiting thesteam generator, can be fed back as input to the TES, thus capturingwaste heat to effectively preheat the input fluid. Waste heat fromanother process may also preheat input fluid to the TES.

According to another aspect, a dynamic insulation system include acontainer having sides, a roof and a lower platform, a plurality ofvertically oriented thermal storage units (TSUs) spaced apart from oneanother, an insulative layer interposed between the plurality of TSUs,the roof and at least one of the sides and floor, a duct formed betweenthe insulative layer and a boundary formed by the sides, an inner sideof the roof and the lower platform of the container, and a blower thatblows unheated air along the air flow path, upward from the platform toa highest portion of the upper portion, such that the air path is formedfrom the highest portion of the roof to the platform, and is heated bythe plurality of TSUs, and output from the TES apparatus. The unheatedair along the flow path forms an insulated layer and is preheated byabsorbing heat from the insulator.

II. Alumina Calcination Applications

This Section II of the Summary relates to the disclosure as it appearsin U.S. Patent Application No. 63/338,805, of which this application isa continuation-in-part application.

The inventive system and process includes a calcination system having athermal energy storage (TES) system that is configured to store thermalenergy derived from a variable renewable energy source havingintermittent availability. The TES system is configured to heat astorage medium using electricity from the renewable energy source, anddeliver heat from the storage medium to a use by circulating a heatedfluid. Further, a calciner is configured to receive and heat a materialstream partially or fully with the heated fluid from the TES system toan activation temperature where impurities in the material stream arethermally decomposed to generate an activated product. Morespecifically, the calcination system is configured to apply the receivedthermal energy by injecting the material stream via a first inlet of thecalciner, and injecting, via a second inlet of the calciner, the heatedfluid from the TES system so as to suspend the injected material streamwithin the calciner.

The calcination system may include a pre-heater configured to pre-heatthe material stream by transferring thermal energy from calcinerreactor's hot exhaust fluid into the material stream, so as to removemoisture from the material stream and increase material temperaturebefore the material stream enters the calciner. The calciner isconfigured to receive the pre-heated material stream and apply thereceived thermal energy to further heat the material stream to a highertemperature than the pre-heated material stream.

According to the calcination system, the TES working fluid, which insome embodiments may be a gaseous mixture consisting of carbon dioxidegas may be circulated from the calciner to the TES system as both thefluid to be heated by the TES system and the fluid to transfer heat tothe material stream within the calciner, In other embodiments, the TESworking fluid and fluid circulating through the calcination system(calcination working fluid) may be distinct streams such that a heatexchanger is utilized to transfer heat indirectly between the TESworking fluid and calcination working fluid. A heat exchanger may beconfigured to receive thermal energy obtained from the calcinationworking fluid, and to apply the thermal energy from the calcinationworking fluid to heat the fluid that is input to the TES system. Thefluid is a non-combustive fluid, and, for example, may be carbondioxide, air, or a mixture of gases. The material stream input to thecalciner includes aluminum hydroxide in mineral form, and the activatedproduct generated by the calciner comprises alumina.

Additionally, a system may be configured where a TES system provides afirst portion of heat to a calciner, and a fuel burner may be configuredto provide the calciner with an additional second source of heat, whichmay be at the same or higher temperature, and wherein a fuel input tothe fuel burner may be at least one of oxyfuel combustion and hydrogen.A heat exchanger may receive the burner exhaust and/or an output heatedfluid from a cooling cyclone that cools the activated product generatedby the calciner, and transfer the heat to a fluid stream that isprovided as an input to the TES system. Further, an electric heater maybe positioned between the TES system and the calciner injection point,and configured to raise the temperature of the fluid output by the TESsystem to a higher temperature. The electric heater may be powered by athermal power turbine generator, whose input heat may be provided by anycombination of fuel combustion, heat from the TES, and recovered heatfrom the integrated calcination/TES system. The TES system may provideheated fluid to the calciner in multiple forms and uses, includingdirectly as heated fluid used within the calciner, or indirectly via aheat exchanger so as to generate steam for use in high-pressure steampartial calcination.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure and are incorporated in andconstitute a part of this specification. The drawings illustrate exampleimplementations of the present disclosure and, together with thedescription, serve to explain the principles of the present disclosure.

In the drawings, similar components and/or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label with a second label thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the second reference label.

FIGS. 1 to 7 appear in parent U.S. patent application Ser. No.18/171,602. FIGS. 8 to 13 include new disclosure of thiscontinuation-in-part application.

FIG. 1 illustrates a schematic diagram of the thermal energy storagesystem architecture according to the example implementations.

FIG. 2 illustrates a schematic diagram of a system according to theexample implementations.

FIG. 3 illustrates a schematic diagram of a storage-fired once-throughsteam generator (OTSG) according to the example implementations.

FIG. 4 illustrates an example view of a system being used as anintegrated cogeneration system according to the example implementations.

FIG. 5 illustrates dynamic insulation according to the exampleimplementations.

FIG. 6 provides an isometric view of the thermal storage unit withmultiple vents closures open, according to some implementations.

FIG. 7 illustrates a two-staged alumina calcination process with anintegrated thermal energy storage (TES) system according to an exampleimplementation;

FIG. 8A illustrates a calciner process with an integrated thermal energystorage (TES) system according to an example implementation;

FIG. 8B illustrates a calciner process with an integrated thermal energystorage (TES) system according to another example implementation;

FIG. 8C illustrates a calciner process with an integrated thermal energystorage (TES) system according to yet another example implementation;

FIG. 9 illustrates a hydrocarbon fuel fired calciner process with anintegrated thermal energy storage (TES) system according to an exampleimplementation;

FIG. 10 illustrates an oxyfuel fired-calciner process with an integratedthermal energy storage (TES) system according to an exampleimplementation;

FIG. 11 illustrates a calciner process with an integrated thermal energystorage (TES) system and optional electric booster according to anexample implementation.

DETAILED DESCRIPTION

Aspects of the example implementations, as disclosed herein, relate tosystems, methods, materials, compositions, articles, and improvementsfor a thermal energy storage system for power generation for variousindustrial applications.

I. Thermal Energy Storage System

This Section I of the Summary relates to the disclosure as it appears inU.S. patent Ser. No. 18/171,602, of which this application is acontinuation-in-part.

U.S. patent Ser. No. 18/171,602 relates to the field of thermal energystorage and utilization systems, and addresses the above-noted problems.A thermal energy storage system is disclosed that stores electricalenergy in the form of thermal energy in a charging mode, and deliversthe stored energy in a discharging mode. The discharging can occur atthe same time as charging; i.e., the system may be heated by electricalenergy at the same time that it is providing a flow of convectivelyheated air. The discharged energy is in the form of hot air, hot fluidsin general, steam, heated CO₂, heated supercritical CO₂, and/orelectrical power generation, and can be supplied to variousapplications, including industrial uses. The disclosed implementationsinclude efficiently constructed, long-service-life thermal energystorage systems having materials, fabrication, physical shape, and otherproperties that mitigate damage and deterioration from repeatedtemperature cycling.

Optionally, heating of the elements of the storage unit may beoptimized, so as to store a maximum amount of heat during the chargingcycle. Alternatively, heating of elements may be optimized to maximizeheating element life, by means including minimizing time at particularheater temperatures, and/or by adjusting peak charging rates and/or peakheating element temperatures. Still other alternatives may balance thesecompeting interests. Specific operations to achieve these optimizationsare discussed further below.

Example implementations employ efficient yet economical thermalinsulation. Specifically, a dynamic insulation design may be used eitherby itself or in combination with static primary thermal insulation. Thedisclosed dynamic insulation techniques provide a controlled flow of airinside the system to restrict dissipation of thermal energy to theoutside environment, which results in higher energy storage efficiency.

System Overview as Disclosed in U.S. patent Ser. No. 18/171,602

FIG. 1 is a block diagram of a system 1 that includes a thermal energystorage system 10, according to one implementation. In theimplementation shown, thermal energy storage system 10 is coupledbetween an input energy source 2 and a downstream energy-consumingprocess 22. For ease of reference, components on the input and outputsides of system 1 may be described as being “upstream” and “downstream”relative to system 10.

In the depicted implementation, thermal energy storage system 10 iscoupled to input energy source 2, which may include one or more sourcesof electrical energy. Source 2 may be renewable, such as photovoltaic(PV) cell or solar, wind, geothermal, etc. Source 2 may also be anothersource, such as nuclear, natural gas, coal, biomass, or other. Source 2may also include a combination of renewable and other sources. In thisimplementation, source 2 is provided to thermal energy storage system 10via infrastructure 4, which may include one or more electricalconductors, commutation equipment, etc. In some implementations,infrastructure 4 may include circuitry configured to transportelectricity over long distances; alternatively, in implementations inwhich input energy source 2 is located in the immediate vicinity ofthermal energy storage system 10, infrastructure 4 may be greatlysimplified. Ultimately, infrastructure 4 delivers energy to input 5 ofthermal energy storage system 10 in the form of electricity.

The electrical energy delivered by infrastructure 4 is input to thermalstorage structure 12 within system 10 through switchgear, protectiveapparatus and active switches controlled by control system 15. Thermalstorage structure 12 includes thermal storage 14, which in turn includesone more assemblages (e.g., 14A, 14B) of solid storage media (e.g., 13A,13B) configured to store thermal energy. These assemblages are variouslyreferred to throughout this disclosure as “stacks,” “arrays,” and thelike. These terms are intended to be generic and not connote anyparticular orientation in space, etc. In general, an array can includeany material that is suitable for storing thermal energy and can beoriented in any given orientation (e.g., vertically, horizontally,etc.). Likewise, the solid storage media within the assemblages mayvariously be referred to as thermal storage blocks, bricks, etc. Inimplementations with multiple arrays, the arrays may be thermallyisolated from one another and are separately controllable, meaning thatthey are capable of being charged or discharged independently from oneanother. This arrangement provides maximum flexibility, permittingmultiple arrays to be charged at the same time, multiple arrays to becharged at different times or at different rates, one array to bedischarged while the other array remains charged, etc.

Thermal storage 14 is configured to receive electrical energy as aninput. The received electrical energy may be provided to thermal storage14 via resistive heating elements that are heated by electrical energyand emit heat, primarily as electromagnetic radiation in the infraredand visible spectrum. During a charging mode of thermal storage 14, theelectrical energy is released as heat from the resistive heatingelements, transferred principally by radiation emitted both by theheating elements and by hotter solid storage media, and absorbed andstored in solid media within storage 14. When an array within thermalstorage 14 is in a discharging mode, the heat is discharged from thermalstorage structure 12 as output 20. As will be described, output 20 maytake various forms, including a fluid such as hot air. (References tothe use of “air” and “gases” within the present disclosure may beunderstood to refer more generally to a “fluid.”) The hot air may beprovided directly to a downstream energy consuming process 22 (e.g., anindustrial application), or it may be passed through a steam generator(not shown) to generate steam for process 22.

Additionally, thermal energy storage system 10 includes a control system15. Control system 15, in various implementations, is configured tocontrol thermal storage 14, including through setting operationalparameters (e.g., discharge rate), controlling fluid flows, controllingthe actuation of electromechanical or semiconductor electrical switchingdevices, etc. The interface 16 between control system 15 and thermalstorage structure 12 (and, in particular thermal storage 14) isindicated in FIG. 1 . Control system 15 may be implemented as acombination of hardware and software in various embodiments.

Control system 15 may also interface with various entities outsidethermal energy storage system 10. For example, control system 15 maycommunicate with input energy source 2 via an input communicationinterface 17B. For example, interface 17B may allow control system 15 toreceive information relating to energy generation conditions at inputenergy source 2. In the implementation in which input energy source 2 isa photovoltaic array, this information may include, for example, currentweather conditions at the site of source 2, as well as other informationavailable to any upstream control systems, sensors, etc. Interface 17Bmay also be used to send information to components or equipmentassociated with source 2.

Similarly, control system 15 may communicate with infrastructure 4 viaan infrastructure communication interface 17A. In a manner similar tothat explained above, interface 17A may be used to provideinfrastructure information to control system 15, such as current orforecast VRE availability, grid demand, infrastructure conditions,maintenance, emergency information, etc. Conversely, communicationinterface 17A may also be used by control system 15 to send informationto components or equipment within infrastructure 4. For example, theinformation may include control signals transmitted from the controlsystem 15, that controls valves or other structures in the thermalstorage structure 12 to move between an open position and a closedposition, or to control electrical or electronic switches connected toheaters in the thermal storage 14. Control system 15 uses informationfrom communication interface 17A in determining control actions, andcontrol actions may adjust closing or firing of switches in a manner tooptimize the use of currently available electric power and maintain thevoltage and current flows within infrastructure 4 within chosen limits.

Control system 15 may also communicate downstream using interfaces 18Aand/or 18B. Interface 18A may be used to communicate information to anyoutput transmission structure (e.g., a steam transmission line), whileinterface 18B may be used to communicate with downstream process 22. Forexample, information provided over interfaces 18A and 18B may includetemperature, industrial application demand, current or future expectedconditions of the output or industrial applications, etc. Control system15 may control the input, heat storage, and output of thermal storagestructure based on a variety of information. As with interfaces 17A and17B, communication over interfaces 18A and 18B may be bidirectional—forexample, system 10 may indicate available capacity to downstream process22. Still further, control system 15 may also communicate with any otherrelevant data sources (indicated by reference numeral 21 in FIG. 1 ) viaadditional communication interface 19. Additional data sources 21 arebroadly intended to encompass any other data source not maintained byeither the upstream or downstream sites. For example, sources 21 mightinclude third-party forecast information, data stored in a cloud datasystem, etc.

Thermal energy storage system 10 is configured to efficiently storethermal energy generated from input energy source 2, and deliver outputenergy in various forms to a downstream process 22. In variousimplementations, input energy source 2 may be from renewable energy anddownstream process 22 may be an industrial application that requires aninput such as steam or hot air. Through various techniques, includingarrays of thermal storage blocks that use radiant heat transfer toefficiently storage energy and a lead-lag discharge paradigm that leadsto desirable thermal properties such as the reduction of temperaturenonuniformities within thermal storage 14, system 10 may advantageouslyprovide a continuous (or near-continuous) flow of output energy based onan intermittently available source. The use of such a system has thepotential to reduce the reliance of industrial applications on fossilfuels.

FIG. 2 provides a schematic view of one implementation of a system 200for storing thermal energy, and further illustrates components andconcepts just described with respect to FIG. 1 . As shown, one or moreenergy sources 201 provide input electricity. For example, and as notedabove, renewable sources such as wind energy from wind turbines 201 a,solar energy from photovoltaic cells 201 b, or other energy sources mayprovide electricity that is variable in availability or price becausethe conditions for generating the electricity are varied. For example,in the case of wind turbine 201 a, the strength, duration and varianceof the wind, as well as other weather conditions causes the amount ofenergy that is produced to vary over time. Similarly, the amount ofenergy generated by photovoltaic cells 201 b also varies over time,depending on factors such as time of day, length of day due to the timeof year, level of cloud cover due to weather conditions, temperature,other ambient conditions, etc. Further, the input electricity may bereceived from the existing power grid 201 c, which may in turn varybased on factors such as pricing, customer demand, maintenance, andemergency requirements.

The electricity generated by source 201 is provided to the thermalstorage structure within the thermal energy storage system. In FIG. 2 ,the passage of electricity into the thermal storage structure isrepresented by wall 203. The input electrical energy is converted toheat within thermal storage 205 via resistive heating elements 207controlled by switches (not shown). Heating elements 207 provide heat tosolid storage media 209. Thermal storage components (sometimes called“bricks”) within thermal storage 205 are arranged to form embeddedradiative chambers. FIG. 2 illustrates that multiple thermal storagearrays 209 may be present within system 200. These arrays may bethermally isolated from one another and may be separately controllable.FIG. 2 is merely intended to provide a conceptual representation of howthermal storage 205 might be implemented—one such implementation might,for example, include only two arrays, or might include six arrays, orten arrays, or more.

In the depicted implementation, a blower 213 drives air or other fluidto thermal storage 205 such that the air is eventually received at alower portion of each of the arrays 209. The air flows upward throughthe channels and chambers formed by bricks in each of the arrays 209,with flow controlled by louvers. By the release of heat energy from theresistive heating elements 207, heat is radiatively transferred toarrays 209 of bricks during a charging mode. Relatively hotter bricksurfaces reradiate absorbed energy (which may be referred to as aradiative “echo”), and participate in heating cooler surfaces. During adischarging mode, the heat stored in arrays 209 is output, as indicatedat 215.

Once the heat has been output in the form of a fluid such as hot air,the fluid may be provided for one or more downstream applications. Forexample, hot air may be used directly in an industrial process that isconfigured to receive the hot air, as shown at 217. Further, hot air maybe provided as a stream 219 to a heat exchanger 218 of a steam generator222, and thereby heats a pressurized fluid such as air, water, CO₂ orother gas. In the example shown, as the hot air stream 219 passes over aline 221 that provides the water from the pump 223 as an input, thewater is heated and steam is generated as an output 225, which may beprovided to an industrial application as shown at 227.

A thermal storage structure such as that depicted in FIGS. 1-2 may alsoinclude output equipment configured to produce steam for use in adownstream application. FIG. 3 , for example, depicts a block diagram ofan implementation of a thermal storage structure 300 that includes astorage-fired once-through steam generator (OTSG). An OTSG is a type ofheat recovery stream generator (HRSG), which is a heat exchanger thataccepts hot air from a storage unit, returns cooler air, and heats anexternal process fluid. The depicted OTSG is configured to use thermalenergy stored in structure 300 to generate steam at output 311.

As has been described, thermal storage structure 300 includes outerstructure 301 such walls, a roof, as well as thermal storage 303 in afirst section of the structure. The OTSG is located in a second sectionof the structure, which is separated from the first section by thermalbarrier 325. During a charging mode, thermal energy is stored in thermalstorage 303. During a discharging mode, the thermal energy stored inthermal storage 303 receives a fluid flow (e.g., air) by way of a blower305. These fluid flows may be generated from fluid entering structure300 via an inlet valve 319, and include a first fluid flow 312A (whichmay be directed to a first stack within thermal storage 303) and asecond fluid flow 312B (which may be directed to a second stack withinthermal storage 303).

As the air or other fluid directed by blower 305 flows through thethermal storage 303 from the lower portion to the upper portion, it isheated and is eventually output at the upper portion of thermal storage303. The heated air, which may be mixed at some times with a bypassfluid flow 312C that has not passed through thermal storage 302, ispassed over a conduit 309 through which flows water or another fluidpumped by the water pump 307. As the hot air heats up the water in theconduit, steam is generated at 311. The cooled air that has crossed theconduit (and transferred heat to the water flowing through it) is thenfed back into the brick heat storage 303 by blower 305. As explainedbelow, the control system can be configured to control attributes of thesteam, including steam quality, or fraction of the steam in the vaporphase, and flow rate.

As shown in FIG. 3 , an OTSG does not include a recirculating drumboiler. Properties of steam produced by an OTSG are generally moredifficult to control than those of steam produced by a more traditionalHRSG with a drum, or reservoir. The steam drum in such an HRSG acts as aphase separator for the steam being produced in one or more heated tubesrecirculating the water; water collects at the bottom of the reservoirwhile the steam rises to the top. Saturated steam (having a steamquality of 100%) can be collected from the top of the drum and can berun through an additional heated tube structure to superheat it andfurther assure high steam quality. Drum-type HRSGs are widely used forpower plants and other applications in which the water circulatingthrough the steam generator is highly purified and stays clean in aclosed system. For applications in which the water has significantmineral content, however, mineral deposits form in the drum and tubesand tend to clog the system, making a recirculating drum designinfeasible.

For applications using water with a higher mineral content, an OTSG maybe a better option. One such application is oil extraction, in whichfeed water for a steam generator may be reclaimed from a water/oilmixture produced by a well. Even after filtering and softening, suchwater may have condensed solid concentrations on the order of 10,000 ppmor higher. The lack of recirculation in an OTSG enables operation in amode to reduce mineral deposit formation; however, an OTSG needs to beoperated carefully in some implementations to avoid mineral deposits inthe OTSG water conduit. For example, having some fraction of waterdroplets present in the steam as it travels through the OTSG conduit maybe required to prevent mineral deposits by retaining the minerals insolution in the water droplets. This consideration suggests that thesteam quality (vapor fraction) of steam within the conduit must bemaintained below a specified level. On the other hand, a high steamquality at the output of the OTSG may be important for the processemploying the steam. Therefore, it is advantageous for a steam generatorpowered by VRE through TES to maintain close tolerances on outlet steamquality. There is a sensitive interplay among variables such as inputwater temperature, input water flow rate and heat input, which must bemanaged to achieve a specified steam quality of output steam whileavoiding damage to the OTSG.

Implementations of the thermal energy storage system disclosed hereinprovide a controlled and specified source of heat to an OTSG. Thecontrolled temperature and flow rate available from the thermal energystorage system allows effective feed-forward and feedback control of thesteam quality of the OTSG output. In one implementation, feed-forwardcontrol includes using a target steam delivery rate and steam qualityvalue, along with measured water temperature at the input to the waterconduit of the OTSG, to determine a heat delivery rate required by thethermal energy storage system for achieving the target values. In thisimplementation, the control system can provide a control signal tocommand the thermal storage structure to deliver the flowing gas acrossthe OTSG at the determined rate. In one implementation, a thermal energystorage system integrated with an OTSG includes instrumentation formeasurement of the input water temperature to the OTSG.

In one implementation, feedback control includes measuring a steamquality value for the steam produced at the outlet of the OTSG, and acontroller using that value to adjust the operation of the system toreturn the steam quality to a desired value. Obtaining the outlet steamquality value may include separating the steam into its liquid and vaporphases and independently monitoring the heat of the phases to determinethe vapor phase fraction. Alternatively, obtaining the outlet steamquality value may include measuring the pressure and velocity of theoutlet steam flow and the pressure and velocity of the inlet water flow,and using the relationship between values to calculate an approximationof the steam quality. Based on the steam quality value, a flow rate ofthe outlet fluid delivered by the thermal storage to the OTSG may beadjusted to achieve or maintain the target steam quality. In oneimplementation, the flow rate of the outlet fluid is adjusted byproviding a feedback signal to a controllable element of the thermalstorage system. The controllable element may be an element used inmoving fluid through the storage medium, such as a blower or other fluidmoving device, a louver, or a valve.

The steam quality measurement of the outlet taken in real time may beused as feedback by the control system to determine the desired rate ofheat delivery to the OTSG. To accomplish this, an implementation of athermal energy storage system integrated with an OTSG may includeinstruments to measure inlet water velocity and outlet steam flowvelocity, and, optionally, a separator along with instruments forproviding separate measurements of the liquid and vapor heat values. Insome implementations, the tubing in an OTSG is arranged such that thetubing closest to the water inlet is positioned in the lowesttemperature portion of the airflow, and that the tubing closest to thesteam exit is positioned in the highest temperature portion of theairflow. In some implementations of the present innovations, the OTSGmay instead be configured such that the highest steam quality tubes(closest to the steam outlet) are positioned at some point midwaythrough the tubing arrangement, so as to enable higher inlet fluidtemperatures from the TSU to the OTSG while mitigating scale formationwithin the tubes and overheating of the tubes, while maintaining propersteam quality. The specified flow parameters of the heated fluidproduced by thermal energy storage systems as disclosed herein may insome implementations allow precise modeling of heat transfer as afunction of position along the conduit. Such modeling may allow specificdesign of conduit geometries to achieve a specified steam qualityprofile along the conduit.

As shown in FIG. 4 , the output of the thermal energy storage system maybe used for an integrated cogeneration system 400. As previouslyexplained, an energy source 401 provides electrical energy that isstored as heat in the heat storage 403 of the TSU. During discharge, theheated air is output at 405. As shown in FIG. 5 , lines containing afluid, in this case water, are pumped into a drum 406 of an HRSG 409 viaa preheating section of tubing 422. In this implementation, HRSG 409 isa recirculating drum type steam generator, including a drum or boiler406 and a recirculating evaporator section 408. The output steam passesthrough line 407 to a superheater coil, and is then provided to aturbine at 415, which generates electricity at 417. As an output, theremaining steam 421 may be expelled to be used as a heat source for aprocess, or condensed at 419 and optionally passed through to adeaeration unit 413 and delivered to pump 411 in order to performsubsequent steam generation.

Certain industrial applications may be particularly well-suited forcogeneration. For example, some applications use higher temperature heatin a first system, such as to convert the heat to mechanical motion asin the case of a turbine, and lower-temperature heat discharged by thefirst system for a second purpose, in a cascading manner; or an inversetemperature cascade may be employed. One example involves a steamgenerator that makes high-pressure steam to drive a steam turbine thatextracts energy from the steam, and low-pressure steam that is used in aprocess, such as an ethanol refinery, to drive distillation and electricpower to run pumps. Still another example involves a thermal energystorage system in which hot gas is output to a turbine, and the heat ofthe turbine outlet gas is used to preheat inlet water to a boiler forprocessing heat in another steam generator (e.g., for use in an oilfieldindustrial application). In one application, cogeneration involves theuse of hot gas at e.g. 840° C. to power or co-power hydrogenelectrolysis, and the lower temperature output gas of the hydrogenelectrolyzer, which may be at about 640° C., is delivered alone or incombination with higher-temperature heat from a TSU to a steam generatoror a turbine for a second use. In another application, cogenerationinvolves the supply of heated gas at a first temperature e.g. 640° C. toenable the operation of a fuel cell, and the waste heat from the fuelcell which may be above 800° C. is delivered to a steam generator or aturbine for a second use, either alone or in combination with other heatsupplied from a TSU.

A cogeneration system may include a heat exchange apparatus thatreceives the discharged output of the thermal storage unit and generatessteam. Alternately, the system may heat another fluid such assupercritical carbon dioxide by circulating high-temperature air fromthe system through a series of pipes carrying a fluid, such as water orCO₂, (which transfers heat from the high-temperature air to the pipesand the fluid), and then recirculating the cooled air back as an inputto the thermal storage structure. This heat exchange apparatus is anHRSG, and in one implementation is integrated into a section of thehousing that is separated from the thermal storage.

The HRSG may be physically contained within the thermal storagestructure, or may be packaged in a separate structure with ductsconveying air to and from the HRSG. The HRSG can include a conduit atleast partially disposed within the second section of the housing. Inone implementation, the conduit can be made of thermally conductivematerial and be arranged so that fluid flows in a “once-through”configuration in a sequence of tubes, entering as lower-temperaturefluid and exiting as higher temperature, possibly partially evaporated,two-phase flow. As noted above, once-through flow is beneficial, forexample, in processing feedwater with substantial dissolved mineralcontaminants to prevent accumulation and precipitation within theconduits.

In an OTSG implementation, a first end of the conduit can be fluidicallycoupled to a water source. The system may provide for inflow of thefluids from the water source into a first end of the conduit, and enableoutflow of the received fluid or steam from a second end of the conduit.The system can include one or more pumps configured to facilitate inflowand outflow of the fluid through the conduit. The system can include aset of valves configured to facilitate controlled outflow of steam fromthe second end of the conduit to a second location for one or moreindustrial applications or electrical power generation. As shown in FIG.6 , an HRSG may also be organized as a recirculating drum-type boilerwith an economizer and optional superheater, for the delivery ofsaturated or superheated steam.

The output of the steam generator may be provided for one or moreindustrial uses. For example, steam may be provided to a turbinegenerator that outputs electricity for use as retail local power. Thecontrol system may receive information associated with local powerdemands, and determine the amount of steam to provide to the turbine, sothat local power demands can be met.

In addition to the generation of electricity, the output of the thermalstorage structure may be used for industrial applications as explainedbelow. Some of these applications may include, but are not limited to,electrolyzers, fuel cells, gas generation units such as hydrogen, carboncapture, manufacture of materials such as cement, calciningapplications, as well as others. More details of these industrialapplications are provided further below.

Dynamic Insulation

It is generally beneficial for a thermal storage structure to minimizeits total energy losses via effective insulation, and to minimize itscost of insulation. Some insulation materials are tolerant of highertemperatures than others. Higher-temperature tolerant materials tend tobe more costly.

FIG. 5 provides a schematic section illustration 500 of animplementation of dynamic insulation. The outer container includes roof501, walls 503, 507 and a foundation 509. Within the outer container, alayer of insulation 511 is provided between the outer container andcolumns of bricks in the stack 513, the columns being represented as 513a, 513 b, 513 c, 513 d and 513 e. The heated fluid that is dischargedfrom the upper portion of the columns of bricks 513 a, 513 b, 513 c, 513d and 513 e exits by way of an output 515, which is connected to a duct517. The duct 517 provides the heated fluid as an input to a steamgenerator 519. Once the heated fluid has passed through the steamgenerator 519, some of its heat is transferred to the water in the steamgenerator and the stream of fluid is cooler than when exiting the steamgenerator. Further, the heated fluid may be used directly in anindustrial process 520 that is configured to receive the heated fluid,as shown at 518. Cooler recycled fluid exits a bottom portion 521 of thesteam generator 519. An air blower 523 receives the cooler fluid, andprovides the cooler fluid, via a passage 525 defined between the walls503 and insulation 527 positioned adjacent the stack 513, through anupper air passage 529 defined between the insulation 511 and the roof501, down through side passages 531 defined on one or more sides of thestack 513 and the insulation 511, and thence down to a passage 533directly below the stack 513.

The air in the passages 525, 529, 531 and 533 acts as an insulatinglayer between (a) the insulations 511 and 527 surrounding the stack 513,and (b) the roof 501, walls 503, 507 and foundation 509. Thus, heat fromthe stack 513 is prevented from overheating the roof 501, walls 503, 507and foundation 509. At the same time, the air flowing through thosepassages 525, 529, 531 and 533 carries by convection heat that maypenetrate the insulations 511 and/or 517 into air flow passages 535 ofthe stack 513, thus preheating the air, which is then heated by passagethrough the air flow passages 535.

The columns of bricks 513 a, 513 b, 513 c, 513 d and 513 e and the airpassages 535 are shown schematically in FIG. 5 . The physical structureof the stacks and air flow passages therethrough in embodimentsdescribed herein is more complex, leading to advantages.

In some implementations, to reduce or minimize the total energy loss,the layer of insulation 511 is a high-temperature primary insulationthat surrounds the columns 513 a, 513 b, 513 c, 513 d and 513 e withinthe housing. Outer layers of lower-cost insulation may also be provided.The primary insulation may be made of thermally insulating materialsselected from any combination of refractory bricks, alumina fiber,ceramic fiber, and fiberglass or any other material that might beapparent to a person of ordinary skill in the art. The amount ofinsulation required to achieve low losses may be large, given the hightemperature differences between the storage media and the environment.To reduce energy losses and insulation costs, conduits are arranged todirect returning, cooler fluid from the HRSG along the outside of aprimary insulation layer before it flows into the storage core forreheating.

The cooler plenum, including the passages 525, 529, 531 and 533, isinsulated from the outside environment, but total temperaturedifferences between the cooler plenum and the outside environment arereduced, which in turn reduces thermal losses. This technique, known as“dynamic insulation,” uses the cooler returning fluid, as describedabove, to recapture heat which passes through the primary insulation,preheating the cooler air before it flows into the stacks of the storageunit. This approach further serves to maintain design temperatureswithin the foundation and supports of the thermal storage structure.Requirements for foundation cooling in existing designs (e.g., formolten salt) involve expensive dedicated blowers andgenerators—requirements avoided by implementations according to thepresent teaching.

The materials of construction and the ground below the storage unit maynot be able to tolerate high temperatures, and in the present systemactive cooling—aided by the unassisted flowing heat exchange fluid inthe case of power failure—can maintain temperatures within designlimits.

A portion of the fluid returning from the HRSG may be directed throughconduits such as element 521 located within the supports and foundationelements, cooling them and delivering the captured heat back to theinput of the storage unit stacks as preheated fluid. The dynamicinsulation may be provided by arranging the bricks 513 a, 513 b, 513 c,513 d and 513 e within the housing so that the bricks 513 a, 513 b, 513c, 513 d and 513 e are not in contact with the outer surface 501, 503,507 of the housing, and are thus thermally isolated from the housing bythe primary insulation formed by the layer of cool fluid. The bricks 513a, 513 b, 513 c, 513 d and 513 e may be positioned at an elevated heightfrom the bottom of the housing, using a platform made of thermallyinsulating material.

During unit operation, a controlled flow of relatively cool fluid isprovided by the fluid blowing units 523, to a region (including passages525, 529, 531 and 533) between the housing and the primary insulation(which may be located on an interior or exterior of an inner enclosurefor one or more thermal storage assemblages), to create the dynamicthermal insulation between the housing and the bricks, which restrictsthe dissipation of thermal energy being generated by the heatingelements and/or stored by the bricks into the outside environment or thehousing, and preheats the fluid. As a result, the controlled flow ofcold fluid by the fluid blowing units of the system may facilitatecontrolled transfer of thermal energy from the bricks to the conduit,and also facilitates dynamic thermal insulation, thereby making thesystem efficient and economical.

In another example implementation, the buoyancy of fluid can enable anunassisted flow of the cold fluid around the bricks between the housingand the primary insulator 511 such that the cold fluid may providedynamic insulation passively, even when the fluid blowing units 523 failto operate in case of power or mechanical failure, thereby maintainingthe temperature of the system within predefined safety limits, toachieve intrinsic safety. The opening of vents, ports, or louvres (notshown) may establish passive buoyancy-driven flow to maintain such flow,including cooling for supports and foundation cooling, during such poweroutages or unit failures, without the need for active equipment.

In the above-described fluid flow, the fluid flows to an upper portionof the unit, down the walls and into the inlet of the stacking,depending on the overall surface area to volume ratio, which is in turndependent on the overall unit size, the flow path of the dynamicinsulation may be changed. For example, in the case of smaller unitsthat have greater surface area as compared with the volume, the amountof fluid flowing through the stack relative to the area may utilize aflow pattern that includes a series of serpentine channels, such thatthe fluid flows on the outside, moves down the wall, up the wall, anddown the wall again before flowing into the inlet. Other channelizationpatterns may also be used.

Additionally, the pressure difference between the return fluid in theinsulation layer and the fluid in the stacks may be maintained such thatthe dynamic insulation layer has a substantially higher pressure thanthe pressure in the stacks themselves. Thus, if there is a leak betweenthe stacks and the insulation, the return fluid at the higher pressuremay be forced into the leak or the cracks, rather than the fluid withinthe stacks leaking out into the dynamic insulation layer. Accordingly,in the event of a leak in the stacks, the very hot fluid of the stacksmay not escape outside of the unit, but instead the return fluid maypush into the stacks, until the pressure between the dynamic insulationlayer in the stacks equalizes. Pressure sensors may be located on eitherside of the blower that provide relative and absolute pressureinformation. With such a configuration, a pressure drop within thesystem may be detected, which can be used to locate the leak.

Earlier systems that store high temperature sensible heat in rocks andmolten salts have required continuous active means of coolingfoundations, and in some implementations continuous active means ofheating system elements to prevent damage to the storage system; thus,continuous active power and backup power supply systems are required. Asystem as described herein does not require an external energy supply tomaintain the safety of the unit. Instead, as described below, thepresent disclosure provides a thermal storage structure that providesfor thermally induced flows that passively cools key elements whenequipment, power, or water fails. This also reduces the need for fans orother cooling elements inside the thermal storage structure.

Forecast-Based System Control

As noted above, forecast information such as weather predictions may beused by a control system to reduce wear and degradation of systemcomponents. Another goal of forecast-based control is to ensure adequatethermal energy production from the thermal energy storage system to theload or application system. Actions that may be taken in view offorecast information include, for example, adjustments to operatingparameters of the thermal energy storage system itself, adjustments toan amount of input energy coming into the thermal energy storage system,and actions or adjustments associated with a load system receiving anoutput of the thermal energy storage system.

Weather forecasting information can come from one or more of multiplesources. One source is a weather station at a site located with thegeneration of electrical energy, such as a solar array or photovoltaicarray, or wind turbines. The weather station may be integrated with apower generation facility, and may be operationally used for controldecisions of that facility, such as for detection of icing on windturbines. Another source is weather information from sources covering awider area, such as radar or other weather stations, which may be fedinto databases accessible to by the control system of the thermal energystorage system. Weather information covering a broader geography may beadvantageous in providing more advanced notice of changes in condition,as compared to the point source information from a weather stationlocated at the power source. Still another possible source of weatherinformation is virtual or simulated weather forecast information. Ingeneral, machine learning methods can be used to train the system,taking into account such data and modifying behavior of the system.

As an example, historical information associated with a power curve ofan energy source may be used as a predictive tool, taking into accountactual conditions, to provide forecasting of power availability andadjust control of the thermal energy storage system, both as to theamount of energy available to charge the units and the amount ofdischarge heat output available. For example, the power curveinformation may be matched with actual data to show that when the poweroutput of a photovoltaic array is decreasing, it may be indicative of acloud passing over one or more parts of the array, or cloudy weathergenerally over the region associated with the array.

Forecast-related information is used to improve the storage andgeneration of heat at the thermal energy storage system in view ofchanging conditions. For example, a forecast may assist in determiningthe amount of heat that must be stored and the rate at which heat mustbe discharged in order to provide a desired output to an industrialapplication—for instance, in the case of providing heat to a steamgenerator, to ensure a consistent quality and amount of steam, and toensure that the steam generator does not have to shut down. Thecontroller may adjust the current and future output of heat in responseto current or forecast reductions in the availability of chargingelectricity, so as to ensure across a period of future time that thestate of charge of the storage unit does not reduce so that heat outputmust be stopped. By adjusting the continuous operation of a steamgenerator to a lower rate in response to a forecasted reduction ofavailable input energy, the unit may operate continuously. The avoidanceof shutdowns and later restarts is an advantageous feature: shuttingdown and restarting a steam generator is a time-consuming process thatis costly and wasteful of energy, and potentially exposes personnel andindustrial facilities to safety risks.

The forecast, in some cases, may be indicative of an expected lowerelectricity input or some other change in electricity input pattern tothe thermal energy storage system. Accordingly, the control system maydetermine, based on the input forecast information, that the amount ofenergy that would be required by the thermal energy storage system togenerate the heat necessary to meet the demands of the steam generatoror other industrial application is lower than the amount of energyexpected to be available. In one implementation, making thisdetermination involves considering any adjustments to operation of thethermal energy storage system that may increase the amount of heat itcan produce. For example, one adjustment that may increase an amount ofheat produced by the system is to run the heating elements in a thermalstorage assemblage at a higher power than usual during periods of inputsupply availability, in order to obtain a higher temperature of theassemblage and greater amount of thermal energy stored. Such“overcharging” or “supercharging” of an assemblage, as discussed furtherbelow, may in some implementations allow sufficient output heat to beproduced through a period of lowered input energy supply. Overchargingmay increase stresses on the thermal storage medium and heater elementsof the system, thus increasing the need for maintenance and the risk ofequipment failure.

As an alternative to operational adjustments for the thermal energystorage system, or in embodiments for which such adjustments are notexpected to make up for a forecasted shortfall of input energy, actionon either the source side or the load side of the thermal energy storagesystem may be initiated by the control system. On the input side, forexample, the forecast difference between predicted and needed inputpower may be used to provide a determination, or decision-support, withrespect to sourcing input electrical energy from other sources during anupcoming time period, to provide the forecasted difference. For example,if the forecasting system determines that the amount of electricalenergy to be provided from a photovoltaic array will be 70% of theexpected amount needed over a given period of time, e.g., due to aforecast of cloudy weather, the control system may effectuate connectionto an alternative input source of electrical energy, such as windturbine, natural gas or other source, such that the thermal energystorage system receives 100% of the expected amount of energy. In animplementation of a thermal energy storage system having an electricalgrid connection available as an alternate input power source, thecontrol system may effectuate connection to the grid in response to aforecast of an input power shortfall.

In a particular implementation, forecast data may be used to determinedesired output rates for a certain number of hours or days ahead,presenting to an operator signals and information relating to expectedoperational adjustments to achieve those output rates, and providing theoperator with a mechanism to implement the output rates as determined bythe system, or alternatively to modify or override those output rates.This may be as simple as a “click to accept” feedback option provided tothe operator, a dead-man's switch that automatically implements thedetermined output rates unless overridden, and/or more detailed optionsof control parameters for the system.

II. Heat Transport in TSU: Bricks and Heating Elements

A. Problems Solved by One or More Disclosed Embodiments

Traditional approaches to the formation of energy storage cells may havevarious problems and disadvantages. For example, traditional approachesmay not provide for uniform heating of the thermal energy storage cells.Instead, they may use structures that create uneven heating, such as hotspots and cold spots. Non-uniform heating may reduce the efficiency ofan energy storage system, lead to earlier equipment failure, causesafety problems, etc. Further, traditional approaches may suffer fromwear and tear on thermal energy storage cells. For example, stressessuch as mechanical and thermal stress may cause deterioration ofperformance, as well as destabilization of the material, such ascracking of the bricks.

B. Example Solutions Disclosed Herein

In some implementations, thermal storage blocks (e.g., bricks) havevarious features that facilitate more even distribution. As one example,blocks may be formed and positioned to define fluid flow pathways withchambers that are open to heating elements to receive radiative energy.Therefore, a given fluid flow pathway (e.g., oriented vertically fromthe top to bottom of a stack) may include two types of openings:radiation chambers that are open to a channel for a heating element andfluid flow openings (e.g., fluid flow slots) that are not open to thechannel. The radiation chambers may receive infrared radiation fromheater elements, which, in conjunction with conductive heating by theheater elements may provide more uniform heating of an assemblage ofthermal storage blocks, relative to traditional implementations. Thefluid flow openings may receive a small amount of radiative energyindirectly via the chambers, but are not directly open to the heatingelement. The stack of bricks may be used alone or in combination withother stacks of bricks to form the thermal storage unit, and one or morethermal storage units may be used together in the thermal energy storagesystem. As the fluid blower circulates the fluid through the structureduring charge and discharge as explained above, a thermocline may beformed in a substantially vertical direction. Further, the fluidmovement system may direct relatively cooler fluid for insulativepurposes, e.g., along the insulated walls and roof of the structure.Finally, a venting system may allow for controlled cooling formaintenance or in the event of power loss, water loss, blower failure,etc., which may advantageously improve safety relative to traditionaltechniques.

Designs according to the present disclosure combine several keyinnovations, which together address these challenges and enable acost-effective, safe, reliable high-temperature thermal energy storagesystem to be built and operated. A carefully structured solid mediasystem according to the present teaching incorporates structured airflowpassages which accomplish effective thermocline discharge; repeatedmixing chambers along the direction of air flow which mitigate thethermal effects of any localized air channel blockages ornonuniformities; effective shielding of thermal radiation frompropagating in the vertical direction; and a radiation chamber structurewhich uniformly and rapidly heats brick material with high heater powerloading, low and uniform exposed surface temperature, and long-distanceheat transfer within the storage media array via multi-step thermalradiation.

Innovative structures according to the present disclosure may comprisean array of bricks that form chambers. The bricks have structured airpassages, such that in the vertical direction air flows upwards in asuccession of open chambers and small air passages. In some embodiments,the array of bricks with internal air passages is organized in astructure such that the outer surface of each brick within the TSU coreforms a wall of a chamber in which it is exposed to radiation from otherbrick surfaces, as well as radiation originating from an electricalheater.

The chamber structure is created by alternating brick materials into acheckerboard-type pattern, in which each brick is surrounded on allsides by open chambers, and each open chamber has adjacent bricks as itswalls. In addition, horizontal parallel passages are provided that passthrough multiple chambers. Electrical heating elements that extendhorizontally through the array are installed in these passages. Anindividual heating element it may be exposed along its length to theinterior spaces of multiple chambers. Each brick within such acheckerboard structure is exposed to open chambers on all sides.Accordingly, during charging, radiant energy from multiple heatingelements heats all outer surfaces of each brick, contributing to therapid and even heating of the brick, and reducing reliance on conductiveheat transfer within the brick by limiting the internal dimensions ofthe brick.

The radiation chamber structure provides a key advance in the design andproduction of effective thermal energy storage systems that are chargedby electrical energy. The large surface area, which is radiativelyexposed to heaters, causes the average temperature of the large surfaceto determine the radiation balance and thus the surface temperature ofthe heater. This intrinsic uniformity enables a high wattage per unitarea of heater without the potential of localized overheating. Andexposed brick surfaces are larger per unit of mass than in priorsystems, meaning that incoming wattage per unit area is correspondinglysmaller, and consequently thermal stresses due to brick internaltemperature differences are lower. And critically, re-radiation ofenergy—radiation by hotter brick surfaces that is absorbed by coolerbrick surfaces—reduces by orders of magnitude the variations in surfacetemperature, and consequently reduces thermal stresses in brickmaterials exposed to radiant heat. Thus, the radiation chamber designeffectively enables heat to be delivered relatively uniformly to a largehorizontally oriented surface area and enables high wattage per unitarea of heater with relatively low wattage per unit area of brick.

Note that while this configuration is described in terms of “horizontal”and “vertical”, these are not absolute degree or angle restrictions.Advantageous factors include maintaining a thermocline and providing forfluid flow through the stack in a direction that results in convectiveheat transfer, exiting the stack at a relatively hotter portion of thethermocline. An additional advantageous factor that may be incorporatedis to position the stack in a manner that encourages buoyant, hot air torise through the stack and exit at the hot end of the thermocline; inthis case, a stack in which the hot end of the thermocline is at ahigher elevation than the cold end of the thermocline is effective, anda vertical thermocline maximizes that effectiveness.

An important advantage of this design is that uniformity of heatingelement temperature is strongly improved in designs according to thepresent disclosure. Any variations in brick heat conductivity, or anycracks forming in a brick that result in changed heat conductivity, arestrongly mitigated by radiation heat transfer away from the locationwith reduced conductivity. That is, a region reaching a highertemperature than nearby regions due to reduced effectiveness of internalconduction will be out of radiation balance with nearby surfaces, andwill as a result be rapidly cooled by radiation to a temperaturerelatively close to that of surrounding surfaces. As a result, boththermal stresses within solid media, and localized peak heatertemperatures, are reduced by a large factor compared to previousteachings.

The system may include one or more air blowing units including anycombination of fans and, blowers, and configured at predefined positionsin the housing to facilitate the controlled flow of air between acombination of the first section, the second section, and the outsideenvironment. The first section may be isolated from the second sectionby a thermal barrier. The air blowing units may facilitate the flow ofair through at least one of the channels of the bricks from the bottomend of the cells to the upper end of the cells in the first section atthe predefined flow rate, and then into the second section, such thatthe air passing through the bricks and/or heating elements of the cellsat the predefined flow rate may be heated to a second predefinedtemperature, and may absorb and transfer the thermal energy emitted bythe heating elements and/or stored by the bricks within the secondsection. The air may flow from the second section across a steamgenerator or other heat exchanger containing one or more conduits, whichcarry a fluid, and which, upon receiving the thermal energy from the airhaving the second predefined temperature, may heat the fluid flowingthrough the conduit to a higher temperature or may convert the fluidinto steam. Further, the system may facilitate outflow of the generatedsteam from the second end of the conduit, to a predefined location forone or more industrial applications. The second predefined temperatureof the air may be based on the material being used in conduit, and therequired temperature and pressure of the steam. In anotherimplementation, the air leaving the second section may be deliveredexternally to an industrial process.

Additionally, the example implementations described herein disclose aresistive heating element. The resistive heating element may include aresistive wire. The resistive wire may have a cross-section that issubstantially round, elongated, flat, or otherwise shaped to admit asheat the energy received from the input of electrical energy.

Passive Cooling

FIG. 6 provides an isometric view of the thermal storage unit withmultiple vent closures open, according to some implementations.Therefore, FIG. 6 may represent a maintenance or failsafe mode ofoperation. As shown, the thermal storage unit also includes an innerenclosure 623. The outer surface of the inner enclosure 623 and theinner surface of the outer enclosure define a fluid passageway throughwhich fluid may be conducted actively for dynamic cooling or passivelyfor failsafe operation.

The inner enclosure 623 includes two vents 615 and 617 which includecorresponding vent closures in some implementations (portions of ventdoor 613, in this example). In some implementations, vents 615 and 617define respective passages between an interior of the inner enclosure623 and an exterior of the inner enclosure. When the external ventclosure 603 is open, these two vents are exposed to the exterior of theouter enclosure as well.

As shown, the vent 615 may vent heated fluid from the thermal storageblocks conducted by duct 619. The vent 617 may allow entry of exteriorfluid into the fluid passageway and eventually into the bottoms of thethermal storage block assemblies via louvers 611 (the vent closure 609may remain closed in this situation). In some implementations, thebuoyancy of fluid heated by the blocks causes it to exit vent 615 and achimney effect pulls external fluid into the outer enclosure via vent617. This external fluid may then be directed through louvers 611 due tothe chimney effect and facilitate cooling of the unit. Speakinggenerally, a first vent closure may open to output heated fluid and asecond vent closure may open to input external fluid for passive ventingoperation.

During passive cooling, the louvers 611 may also receive external fluiddirectly, e.g., when vent closure 609 is open. In this situation, bothvents 615 and 617 may output fluid from the inner and outer enclosures.

Vent door 613 in the illustrated implementation, also closes an input tothe steam generator when the vents 615 and 617 are open. This mayprevent damage to steam generator components (such as water tubes) whenwater is cut off, the blower is not operating, or other failureconditions. The vent 617 may communicate with one or more blowers whichmay allow fluid to passively move through the blowers even when they arenot operating. Speaking generally, one or more failsafe vent closure mayclose one or more passageways to cut off fluid heated by the thermalstorage blocks and reduce or avoid equipment damage.

When the vent door 613 is closed, it may define part of the fluidpassageway used for dynamic insulation. For example, the fluid movementsystem may move fluid up along one wall of the inner enclosure, acrossan outer surface of the vent door 613, across a roof of the innerenclosure, down one or more other sides of the inner enclosure, and intothe thermal storage blocks (e.g., via louvers 611). Louvers 611 mayallow control of fluid flow into assemblages of thermal storage blocks,including independent control of separately insulated assemblages insome implementations.

In the closed position, vent door 613 may also define an input pathwayfor heated fluid to pass from the thermal storage blocks to the duct 619and beneath the vent door 613 into the steam generator to generatesteam.

In some implementations, one or more of vent door 613, vent closure 603,and vent closure 609 are configured to open in response to anonoperating condition of one or more system elements (e.g.,nonoperation of the fluid movement system, power failure, water failure,etc.). In some implementations, one or more vent closures or doors areheld in a closed position using electric power during normal operationand open automatically when electric power is lost or in response to asignal indicating to open.

In some implementations, one or more vent closures are opened while afluid blower is operating, e.g., to rapidly cool the unit formaintenance.

Thermoelectric Power Generation

1. Problems to be Solved

Gasification is the thermal conversion of organic matter by partialoxidation into gaseous product, consisting primarily of H₂, carbonmonoxide (CO), and may also include methane, water, CO₂ and otherproducts. Biomass (e.g. wood pellets), carbon rich waste (e.g. paper,cardboard) and even plastic waste can be gasified to produce hydrogenrich syngas at high yields with high temperature steam, with optimumyields attained at >1000° C. The rate of formation of combustible gasesare increased by increasing the temperature of the reaction, leading toa more complete conversion of the fuel. The yield of hydrogen, forexample, increases with the rise of reaction temperature.

Turning waste carbon sources into a useable alternative energy orfeedstock stream to fossil fuels is a potentially highly impactfulmethod for reducing carbon emissions and valorizing otherwise unusedcarbon sources.

2. Thermoelectric Power Generation

Indirect gasification uses a Dual Fluidized Bed (DFB) system consistingof two intercoupled fluidized bed reactors—one combustor and onegasifier—between which a considerable amount of bed material iscirculated. This circulating bed material acts as a heat carrier fromthe combustor to the gasifier, thus satisfying the net energy demand inthe gasifier originated by the fact that it is fluidized solely withsteam, i.e. with no air/oxygen present, in contrast to the classicalapproach in gasification technology also called direct gasification. Theabsence of nitrogen and combustion in the gasifying chamber implies thegeneration of a raw gas with much higher heating value than that indirect gasification. The char which is not converted in the gasifyingchamber follows the circulating bed material into the combustor, whichis fluidized with air, where it is combusted and releases heat which iscaptured by the circulating bed material and thereby transported intothe gasifier in order to close the heat balance of the system.

Referring to FIG. 4 , in some example implementations, the thermalenergy storage structure 403 can be integrated directly with a steampower plant to provide an integrated cogeneration system 400 for acontinuous supply of hot air, steam and/or electrical power for variousindustrial applications. Thermal storage structure 403 may beoperatively coupled to electrical energy sources 401 to receiveelectrical energy and convert and store the electrical energy in theform of thermal energy. In some implementations, at least one of theelectrical energy sources 401 may comprise an input energy source havingintermittent availability. However, electrical energy sources 401 mayalso include input energy sources having on-demand availability, andcombinations of intermittent and on-demand sources are also possible andcontemplated. The system 403 can be operatively coupled to a heatrecovery steam generator (HRSG) 409 which is configured to receiveheated air from the system 403 for converting the water flowing throughconduits 407 of the HRSG 409 into steam for the steam turbine 415. In analternative implementation, HRSG 409 is a once-through steam generatorin which the water used to generate steam is not recirculated. However,implementations in which the water used to generate steam is partiallyor fully circulated as shown in FIG. 4 are also possible andcontemplated.

A control unit can control the flow of the heated air (and moregenerally, a fluid) into the HRSG 409, based on load demand, cost perKWH of available energy source, and thermal energy stored in the system.The steam turbine 415 can be operatively coupled to a steam generator409, which can be configured to generate a continuous supply ofelectrical energy. Further, the steam turbine 415 can also release acontinuous flow of relatively lower-pressure 421 steam as output tosupply an industrial process. Accordingly, implementations are possibleand contemplated in which steam is received by the turbine at a firstpressure and is output therefrom at a second, lower pressure, with lowerpressure steam being provided to the industrial process. Examples ofsuch industrial process that may utilize the lower pressure output steaminclude (but are not limited to) production of liquid transportationfuels, including petroleum fuels, biofuel production, production ofdiesel fuels, production of ethanol, grain drying, and so on.

The production of ethanol as a fuel from starch and cellulose involvesaqueous processes including hydrolysis, fermentation and distillation.Ethanol plants have substantial electrical energy demand for processpumps and other equipment, and significant demands for heat to drivehydrolysis, cooking, distillation, dehydrating, and drying the biomassand alcohol streams. It is well known to use conventional electric powerand fuel-fired boilers, or fuel-fired cogeneration of steam and power,to operate the fuel production process. Such energy inputs are asignificant source of CO₂ emissions, in some cases 25% or more of totalCO₂ associated with total agriculture, fuel production, andtransportation of finished fuel. Accordingly, the use of renewableenergy to drive such production processes is of value. Some ethanolplants are located in locations where excellent solar resources areavailable. Others are located in locations where excellent wind andsolar resources are available.

The use of electrothermal energy storage may provide local benefits insuch locations to grid operators, including switchable electricity loadsto stabilize the grid; and intermittently available grid electricity(e.g. during low-price periods) may provide a low-cost continuous sourceof energy delivered from the electrothermal storage unit.

The use of renewable energy (wind or solar power) as the source ofenergy charging the electrothermal storage may deliver importantreductions in the total. CO₂ emissions involved in producing the fuel,as up to 100% of the driving electricity and driving steam required forplant operations may come from cogeneration of heat and power by a steamturbine powered by steam generated by an electrothermal storage unit.Such emissions reductions are both valuable to the climate andcommercially valuable under programs which create financial value forrenewable and low-carbon fuels.

The electrothermal energy storage unit having air as a heat transferfluid may provide other important benefits to an ethanol productionfacility, notably in the supply of heated dry air to process elementsincluding spent grain drying. One useful combination of heated airoutput and steam output from a single unit is achieved by directing theoutlet stream from the HRSG to the grain dryer. In this manner, a givenamount of energy storage material (e.g. brick) may be cycled through awider change in temperature, enabling the storage of extra energy in agiven mass of storage material. There may be periods where the energystorage material temperature is below the temperature required formaking steam, but the discharge of heated air for drying or otheroperations continues.

In some implementations thermal storage structure 403 may be directlyintegrated to industrial processing systems in order to directly deliverheat to a process without generation of steam or electricity. Forexample, thermal storage structure 403 may be integrated into industrialsystems for manufacturing lime, concrete, petrochemical processing, orany other process that requires the delivery of high temperature air orheat to drive a chemical process. Through integration of thermal storagestructure 403 charged by VRE, the fossil fuel requirements of suchindustrial process may be significantly reduced or possibly eliminated.

The control unit can determine how much steam is to flow through acondenser 419 versus steam output 421, varying both total electricalgeneration and steam production as needed. As a result, the integratedcogeneration system 400 can cogenerate steam and electrical power forone or more industrial applications.

If implemented with an OTSG as shown in FIG. 3 instead of therecirculating HRSG shown in FIG. 5 , the overall integrated cogenerationsystem 400 can be used as thermal storage once-through steam generator(TSOTG) which can be used in oil fields and industries to deliver wetsaturated steam or superheated dry steam at a specific flow rate andsteam quality under automated control. High temperature delivered by thebricks and heating elements of the system 403 can power the integratedheat recovery steam generator (HRSG) 409. A closed air recirculationloop can minimize heat losses and maintain overall steam generationefficiency above 98%.

The HRSG 409 can include a positive displacement (PD) pump 411 undervariable frequency drive (VFD) control to deliver water to the HRSG 409.Automatic control of steam flow rate and steam quality (includingfeed-forward and feed-back quality control) can be provided by the TSOTG400. In an exemplary example implementation, a built-in Local OperatorInterface (LOI) panel operatively coupled to system 400 and the controlunit can provide unit supervision and control. Further, thermal storagestructure 403 can be connected to a supervisory control and dataacquisition system (SCADA)) associated with the steam power plant (orother load system). In one implementation, a second electrical powersource is electrically connected to the steam generator pumps, blowers,instruments, and control unit.

In some implementations, system 400 may be designed to operate usingfeedwater with substantially dissolved solids; accordingly, arecirculating boiler configuration is impractical. Instead, aonce-through steam generation process can be used to deliver wet steamwithout the buildup of mineral contaminants within the boiler. Aserpentine arrangement of conduits 407 in an alternative once-throughconfiguration of the HRSG 409 can be exposed to high-temperature airgenerated by the thermal storage structure 403, in which preheating andevaporation of the feedwater can take place consecutively. Water can beforced through the conduits of HRSG 409 by a boiler feedwater pump,entering the HRSG 409 at the “cold” end. The water can change phasealong the circuit and may exit as wet steam at the “hot” end. In oneimplementation, steam quality is calculated based on the temperature ofair provided by the thermal storage structure 403, and feedwatertemperatures and flow rates, and is measured based on velocityacceleration at the HRSG outlet. Embodiments implementing a separator toseparate steam from water vapor and determine the steam quality based ontheir relative proportions are also possible and contemplated.

In the case of an OTSG implementation, airflow (or other fluid flow) canbe arranged such that the hottest air is nearest to the steam outlet atthe second end of the conduit. An OTSG conduit can be mountedtransversely to the airflow path and arranged in a sequence to providehighly efficient heat transfer and steam generation while achieving alow cost of materials. As a result, other than thermal losses fromenergy storage, steam generation efficiency can reach above 98%. Theprevention of scale formation within the tubing is an important designconsideration in the selection of steam quality and tubing design. Aswater flows through the serpentine conduit, the water first rises intemperature according to the saturation temperature corresponding to thepressure, then begins evaporating (boiling) as flow continues throughheated conduits.

As boiling occurs, volume expansion causes acceleration of the rate offlow, and the concentration of dissolved solids increases proportionallywith the fraction of liquid phase remaining. Maintaining concentrationsbelow precipitation concentration limits is an important considerationto prevent scale formation. Within a bulk flow whose average mineralprecipitation, localized nucleate and film boiling can cause increasedlocal mineral concentrations at the conduit walls. To mitigate thepotential for scale formation arising from such localized increases inmineral concentration, conduits which carry water being heated may berearranged such that the highest temperature heating air flows acrossconduits which carry water at a lower steam quality, and that heatingair at a lower-temperature flows across the conduits that carry thehighest steam quality flow.

Returning to FIG. 4 , various implementations are contemplated in whicha fluid movement device moves fluid across a thermal storage medium, toheat the fluid, and subsequently to an HRSG such as HRSG 409 for use inthe generation of steam. In one implementation, the fluid is air.Accordingly, air circulation through the HRSG 409 can be forced by avariable-speed blower, which serves as the fluid movement device in suchan embodiment. Air temperature can be adjusted by recirculation/mixing,to provide inlet air temperature that does not vary with the state ofcharge of the bricks or other mechanisms used to implement a thermalstorage unit. The HRSG 409 can be fluidically coupled to a steam turbinegenerator 415, which upon receiving the steam from the HRSG 409, causesthe production of electrical energy using generator 417. Further, thesteam gas turbine 415 in various embodiments releases low-pressure steamthat is condensed to a liquid by a condenser 419, and then de-aeratedusing a deaeration unit 413 and delivered to pump 411 in order toperform subsequent steam generation.

III. Calciner

1. Problems to be Solved

To address the problems and disadvantages of conventional calcinationnoted above, the thermal energy storage system described herein suppliesheat to recirculating process steam, and may be integrated with heatrecovery apparatuses to address art plant balance problems. For example,heat from the hot flue gases of the second gas suspension calciner maybe utilized to supply a portion of the heat to either the thermalstorage working fluid medium (e.g., gas-to-gas heat exchangers) or theprocess steam (e.g., gas to liquid heat exchanger). This will allow theplant greater flexibility in energy management as well as maintenance tofix solid buildup in heat transfer equipment. The thermal battery may beexternal to the plant and may either supply steam externally with anattached steam generator or supply steam indirectly, passing hot gasesthrough existing or new heat exchangers replacing the duty of combustiongas products.

In another example implementation, the thermal storage relates to afully integrated process where the thermal batteries replace allcombustion on site. This implementation includes the above-describedapproach, with supplying all or the majority of the heat to the secondcalcination stage. The temperature of the partially calcined material isbrought to near ambient pressure (from the high-pressure stage 1) andput in direct contact with hot flue gases, bringing the temperature to850-950 C. This reduced temperature range allows the heat from firedfuels to be replaced by high temperature stored heat.

In some example implementations, the primary working fluid of thethermal energy storage system would contact the material to be calcined.In other example implementations, this heating may occur indirectly,where the primary working fluid of the thermal battery does not directlycontact the material. The hot gas would be blown through the calciner atsufficiently high velocities to achieve desired level of suspension andactivation. The gas effluent would leave the chamber at a hightemperature to be used in the steam generation and superheating of theprocess steam used in the first stage of calcination as well as anyother steam needs in the system.

2. Application of Calciner to Thermal Energy Storage System

In implementations that employ direct heat transfer, the fluid used asthe heat transfer medium in the TES system is being supplied directly tothe raw material in the calciner and then recirculated back to the TESsystem after coming into direct contact with the raw material. Inimplementations that employ indirect heat transfer, the fluid used inthe TES system does not come into direct, physical contact with thematerial in the material heating system. Rather, in someimplementations, the fluid in the TES system is used to transfer thermalenergy via a heat exchanger into a secondary fluid that comes intocontact the material. In other implementations, the fluid used in theTES system may indirectly heat the raw material without the presence ofa secondary fluid by heating the walls of the calciner or kiln reactorsystem, with the heated walls transferring heat to the raw material onthe other side of the wall via conduction and radiation. This “indirect”heating mode of thermal storage operation can also be used inapplications other than calcination or kiln reactors, including but notlimited to biomass drying or food processing. The secondary fluid may bein the liquid state in some implementations.

As noted above, the TES system may be used to provide heat into thecalcination step of the Bayer alumina process. Additionally, the heatinputs into other parts of the process may also replace fuel, includingthe fuel that is provided at the mine, at the lime kiln, and at thesteam generator that provides energy to operate these modules.

These approaches may have problems and disadvantages. For example, whensteam is used as a heat transfer medium in calcination stage, it isnecessary to account for the plant balance, as the extremely high massflow of superheated high-pressure steam must be filtered and cleanedbefore recirculating to other areas of the plant. The theoretically morefavorable heat balance from collecting high temperature moisture fromthe decomposer also translates to a more complex, integrated process.The large mass flow leads to art problems in supplying the correctquantity of superheated steam. The steam generator/superheater is amajor area for concern, both from the thermodynamic and operatingstandpoint. Additional fuel must be fired in this step. Additionally,buildup in process equipment is one of the largest issues in theconcept, as the recirculated steam often must be cleaned and filtered ofparticulate matter before interacting with the steam generator andsuperheater.

To address these problems and disadvantages, the thermal energy storagesystem described above supplies heat to recirculating process steam, andmay be integrated with heat recovery apparatuses to address art plantbalance problems. For example, heat from the hot flue gases of thesecond gas suspension calciner may be utilized to supply a portion ofthe heat to either the thermal storage working fluid medium (e.g.,gas-to-gas heat exchangers) or the process steam (e.g., gas to liquidheat exchanger). This will allow the plant greater flexibility in energymanagement as well as maintenance to fix solid buildup in heat transferequipment. The thermal battery may be external to the plant and mayeither supply steam externally with an attached steam generator orsupply steam indirectly, passing hot gases through existing or new heatexchangers replacing the duty of combustion gas products.

In another example implementation, the thermal storage relates to afully integrated process where the thermal batteries replace allcombustion on site. This implementation includes the above-describedapproach, with supplying all or the majority of the heat to the secondcalcination stage. The temperature of the partially calcined material isbrought to near ambient pressure (from the high-pressure stage 1) andput in direct contact with hot flue gases bringing the temperature to850-950 C. This reduced temperature range allows the heat from firedfuels to be replaced by high temperature stored heat.

The two-stage pressure calcination stage of the Bayer process is oneknown process. More commonly, the calcination stage consists of onestage (which is essentially identical to the second ‘low-pressure’ stageof the aforementioned two-stage process) where wet gibbsite from theprecipitation stage prior is roasted up to 1100° C. in order to driveoff both free moisture and chemically bound moisture in order to producealumina solids. It resembles clay calcination in process design, withdifferences in reaction temperatures and quality specifications.Further, while clay calcination requires a reducing zone, aluminacalcination does not require a reducing zone.

A variety of calcination technologies may be used for this aluminacalcination heating, including rotary kilns, gas suspension calciners,and fluidized bed calciners. An alumina calcination plant may include aseries of preheater cyclones where the material is dropped through aseries of cyclones with hot gas from the calciner or furnace rising andpreheating the material to the reaction temperature. This stage bothheats up the raw material to reaction temperature and evaporates freemoisture in the material. The preheated solid material is then droppedinto the calcination reactor (rotary kiln, calciner, etc.). Here it isheated to a temperature of approximately 1100° C., where the chemicallybound water is released, creating anhydrous alumina.

Traditionally, a fossil fuel (e.g., natural gas) is burned at the baseof the furnace, generating hot gases to transfer heat both convectivelyand radiatively to the material feed. Often, for heat recovery purposes,the calcined raw material is cooled in cooling cyclones where ambientair directly contacts the calcined alumina exchanging heat, cooling thealumina to near ambient temperatures. The heated ambient air used tocool the alumina may be supplied to meet other heat demands in theprocess. This can be used as preheated combustion air for the burners,or in the case of gas suspension or fluidized bed calciners, as the airflow which maintains sufficient velocities to fluidize or suspend thesolid material throughout the calciner and preheat stages of theprocess. In both cases, heat from the thermal storage unit enables lessfuel to be burned to both maintain sufficient gas flow and reactiontemperatures. The alumina may be further cooled with water in heatexchangers indirectly in conjunction with cooling air.

In some example implementations, the primary working fluid of thethermal energy storage system would contact the material to be calcined.In other example implementations, this heating may occur indirectly,where the primary working fluid of the thermal battery does not directlycontact the material. The hot gas would be blown through the calciner atsufficiently high velocities to achieve desired level of suspension andactivation. The gas effluent would leave the chamber at a hightemperature to be used in the steam generation and superheating of theprocess steam used in the first stage of calcination as well as anyother steam needs in the system.

As shown in FIG. 7 , a calciner process 700 associated with aluminumproduction according to the example implementations has severalmodifications to prior approaches. The thermal energy storage 701provides a heat input to the second calcination stage 703. Thus, insteadof using fuel to generate that heat, such as by combustion in otherapproaches, the heat is provided as hot gas heated by the TES system asexplained above a high volume of high temperature hot gas is provided asan input to the second calcination stage at its operating temperature.Thus, it is not necessary to provide preheated air from alumina cooling711, as may be required in prior approaches.

The output byproduct of the second calcination stage 703 is slightlycooled gas that can be used for the heat recovery steam generator 707,instead of the additional fuel and air that may be present in the priorapproaches. The steam output from the steam generator 707 is provided tothe first calcination unit 709 at the temperature of the firstcalcination unit 709, which may provide the recycled steam flow andsolids as in the prior art. Additionally, instead of expelling excessheat or waste heat from the steam generator as a set gas, the heatbyproduct of the steam generator is the gas that has passed through aheat recovery zone, and is injected into the alumina cooling cyclones711, along with ambient air. The byproduct heat from the alumina coolingcyclones is provided, through a baghouse and filter 717, as therecirculated gas for the input of the thermal storage unit. According toan alternative implementation, the TES system may only be used forproviding the heat for the steam generator, so that the existinginfrastructure of the alumina processing facility can be used withoutsubstantial modification.

The example material activation system may have various benefits andadvantages. For example, because the output of the waste heat recoveryis recirculated as an input to the thermal energy storage, emission ofheat through the stack is avoided. Thus, unnecessary heat emissions tothe atmosphere can be avoided. Additionally, by using the incoming heatfrom the TES system, it is not necessary to use fossil fuel to providethe input heat. Further, because the combustion aspect of generatingheat is removed, the free moisture in the input combustion stream iseliminated, which avoids the problems introduced by the presence of thatmoisture, particularly with respect to the calcination of clay, asexplained above. The example implementation also has a benefit of morefavorable thermodynamics and lower maximum temperatures.

Inventive Concept

Innovations are disclosed in the following discussion in which anelectric-to-thermal energy storage system provides direct heat to analumina calcination process. A portion of the added heat would berecirculated to the thermal energy storage system instead of beingexhausted to the environment which is the case in fired calcinationprocesses of conventional systems. The innovative designs enable zero-or low-carbon alumina calcination by reducing overall energy demand ofthe process via waste gas recirculation and by allowing heat to beprovided from an intermittent charging from electricity. If renewableelectricity is used to charge the thermal energy storage system, itenables the process to be zero-carbon. The invention may also enablemore favorable thermodynamic conditions for the reaction to occur bybeing able to inject hot gas of any mixture of molecular components(e.g. air, pure CO₂, etc.). This serves the purpose of creating athermodynamically favorable environment for the dehydroxylation reactionto take place by minimizing water vapor content (which exists incombustion) and (in the CO₂ thermal storage working fluid case forexample) allows for more favorable heat transfer kinetics due to theability of CO₂ to participate in radiative heat transfer.

The thermal energy storage (TES) system may inject a hot gas to supplyor some of the heat that would otherwise be supplied to the raw materialvia firing hydrocarbon fuel in a burner.

In one implementation of the invention, the design allows for convertingan existing calcination process into an oxyfuel-fired case for thepurpose of easy carbon dioxide capture for recirculation in the TES andfor export to an enhanced oil recovery (EOR) application, industrialuse, or sequestration. Converting to oxyfuel without the TES integrationwould require a new process configuration and new plant. Many aluminacalcination processes are very dependent on having sufficient gas flowto suspend the raw material to promote proper material flow through theplant and to enable sufficient heat transfer between the gas and rawmaterial.

In a traditional plant being converted to oxyfuel, there are two placeswhere gas flow is negatively affected. The first is that the cooling airis often heated by the activated material before being introduced to thecalciner and preheater to suspend and heat the raw material. In anoxyfuel case, its purpose would be defeated by introducing ambient airto the process, since the exit gas mixture would not be pure water vaporand carbon dioxide hence making carbon capture energy intensive andexpensive. The result is that a large portion of the hot gas flowintroduced is excluded from the heating stages of the process.

Additionally, oxyfuel combustion generates fewer combustion products peramount of heat provided due to the flame not having to heat inertcomponents of air such as nitrogen. The thermal energy storage systemdepicted in FIG. 10 allows an oxyfuel process with relatively minimalintrusion to traditional processes. The missing hot gas from the coolingair and traditional combustion is replaced with hot gas from storedintermittent electric charging. In addition, the overall thermalefficiency of the process is improved due to the carbon dioxiderecirculating through the storage system. More specifically, exposingthe raw material to a stream with majority carbon dioxide may improvekinetics and thermodynamics of the reaction due to carbon dioxide'sability as a polar molecule to participate in radiative heat transfer aswell as reducing the water vapor partial pressure compared toconventional systems, making the hydroxylation reaction morethermodynamically favorable.

The same advantage is achieved if the primary burner is converted toburn pure hydrogen. The resulting combustion products are mostly watervapor, although, as in the oxyfuel case, less flue gas volume isproduced per unit heat provided. In this implementation, the cooling aircan be utilized, since there is no capturable carbon dioxide gas, andthe thermal energy storage system can supply additional high-temperatureair to allow for sufficient gas flows and heat delivery to the rawmaterial in a conventional system's calcination process. In this case,the TES system would not need to recirculate nearly pure carbon dioxide.The implementation would resemble the process depicted in FIG. 9 , withthe only modification being that the “hydrocarbon” fuel is hydrogen.After water knock-out and particulate/fines (e.g., finely crushed orpowdered material) removal, a portion of the gas is recirculated backinto the TES system.

Advantages provided by the present innovative systems and processesinclude the enabling design for high-temperature activation/calcinationof alumina to become less carbon intensive in an efficient manner (i.e.,without extensively altering existing physical systems and processes).Additionally, the design improves the energy intensity of the aluminacalcination process, and alleviates plant constraints, such as requiredgas flow rates, which enables relatively simple conversion toalternative combustion techniques such as oxy-fuel or hydrogen burners.This reduces the direct emissions tied to the calcination process,either by easy carbon capture techniques (oxyfuel) or by eliminating theuse of hydrocarbons (hydrogen). Optionally, the hydrogen and/or oxygenmay be provided (or supplemented) by a solid oxide electrolysis or solidoxide fuel cell.

Systems and Processes

The above advantages are achieved as follows: first, the innovativesystem lowers the carbon intensity of the process by using heat fromelectric sources to replace heat otherwise provided by burninghydrocarbon fuel. Using intermittent electric charging of the thermalenergy storage unit allows energy from renewables such as wind and solarbe used in providing continuous heat to the calcination process in a waythat does not require a drastically different plant process. The impacton the plant process can be emphasized in viewing FIGS. 8C, 10 and 11 .In comparing these process flows to conventional processes, an importantchange is the number of burners and the presence of the thermal energystorage system, along with the tie-in, which reroutes a portion of thegas heading to the stack exhaust to the thermal energy storage systeminlet fluid.

The raw material can still be heated convectively through mixing withhot gas. Calciners and preheating sections in conventional systems mayrequire some modification, but these modifications are minimal comparedto alternative carbon free options such as using electric heatersdirectly in the mix or converting to oxyfuel or hydrogen. In otherprocesses (depicted in FIG. 7 ), the thermal storage unit can provideheat to the process as direct hot gas or as steam generation for use ina high-pressure steam partial calcination stage before the traditionalhigh temperature stage 2, where hot gas is introduced to the system tosupplement or replace the duty of fired heat from a burner.

The energy intensity is improved in one of two ways. The first one ishaving the ability to control the reaction atmosphere. The thermalenergy storage (TES) system may be able to circulate any mixture ofgases, whether that be a pure substance such as CO₂ or a mixture such asair or recirculated flue gas products. This enhanced atmosphere controlallows the underlying reaction to be more thermodynamically favored. Inthe alumina case, the main reaction is hydroxylation, where chemicallybound water is released as vapor at high temperatures. In an environmentthat minimizes the partial pressure of water vapor, the desired reactiondirection is thermodynamically favored, reducing the temperaturerequirement of the activation.

The second (and more significant) way is through the thermal energystorage system accepting input gas at a temperature between ambient and200° C. Once the gas stream is filtered and water is removed, the gasstream exiting the preheating/drying stage of the process can be routedback into the thermal energy storage (TES) system. This saves sensibleheat of heating gas at ambient temperature from ambient conditions (e.g.20° C.) to the hot gas temperature to the calcination heating process(e.g. >900° C.). This heat would otherwise be expelled to theenvironment in a conventional fired process, due to the relatively lowtemperature of the gas.

One way to reduce the carbon emissions is by using oxy-fired or oxyfuelcombustion. This means that oxygen is generated externally (usually inan air separation unit) and is fired with the fuel (such as naturalgas). The resulting flue contains only H₂O and CO₂, since the othercomponents of air are separated out in the air separation unit. The mainpurpose of this is to enable easy carbon capture of a fired process.

Water can easily be separated from CO₂ due to water condensing atambient temperatures. CO₂ removal is much more difficult (e.g., energyintensive and expensive) when other components of air are present in thestream. The oxygen combustion heats the raw material as the thermalstorage unit injects more high-temperature recirculated CO₂. Here, theprimary burner would supply the highest temperature heat radiatively andconvectively, with all supplementary heat being supplied by the hotfluid injection from the thermal energy storage (TES) system.

The cooling stage, which normally provides high-temperature,high-velocity gas flow, can be advantageously separated from the processtrain, in order to avoid mixing ambient air with the pure CO₂ and watervapor stream. The heated ambient cooling air may indirectly exchangeheat with the thermal storage unit inlet flow of nearly pure CO₂ or beused to preheat water for steam generation for use elsewhere in theplant, or for power generation.

Additionally, oxy-fired combustion results in higher temperatures andlower flue gas flow rates. The gas flow of the modified system may beinsufficient to suspend or lift the raw material in the process. Thethermal energy storage (TES) system injects sufficient gas into thecalciner to provide the necessary heat for the reaction to proceed. Theflue gas and the injected air from the TES unit would mix and flow upthrough the process preheating raw material above the calciner.Eventually, the water is knocked out of the stream by condensation(lowering the temperature of the gas stream) and a pure CO₂ streamremains. A portion of the CO₂ is recirculated into the TES unit, withthe remaining portion able to be compressed and transported for use inan industrial application, sequestered, or in EOR. A schematic of theoxyfuel case is depicted in FIG. 10 .

The TES system can supply heat and integrate to the alumina calcinationprocess in a means similar to its integration into a clay calcinationprocess. Combustion in burners may be reduced or eliminated with themajority or all the heat input to the system coming from the thermalenergy storage system. Hot gas that has been heated by the thermalenergy storage system may be injected to contact and interact with theraw material. This gas may be air or another working fluid such as CO₂or a mixture in any proportion of gases including air, oxygen, and CO₂.

One implementation, shown in FIG. 9 , has the TES system providing afirst portion of the process heat and a fuel burner providing a secondportion. In this example, the thermal energy storage system reduces thefuel consumption of the burners, and a portion of the exhaust gas thatis normally released to the environment after particulate filtering isrecirculated back into the thermal energy storage system for reheating.The gas being passed through the thermal energy storage system may alsoinclude air from the environment in order to control temperature andmodulate the gas mixtures chemical composition.

The use of CO₂ as the heat transfer gas from the thermal storage unit tothe process is beneficial in the case in which the overall system isdesigned or converted to drive combustion with nearly pure oxygen. Thismethod of burning is generally referred to as oxy-fired or oxyfuelcombustion. In such instances, oxygen may be generated externally(usually in an air separation unit) and is fired with the fuel (such asnatural gas). The resulting flue primarily contains only H₂O and CO₂ asthe other components of air are separated out in the air separationunit. The main purpose of this is in enabling easy carbon capture fromthe exhaust of a fired process without requiring nitrogen separation.Water can be easily separated from CO₂ due to water condensing atambient temperatures. CO₂ removal is much more difficult (energyintensive and expensive) when other components of air are present in thestream. By carrying heat from the thermal energy storage system in a CO₂stream, and using oxy-fuel combustion, very high temperatures may beachieved without subsequent costs of gas separation for CO₂ capture. Inone implementation, a fuel-fired burner would supply thehighest-temperature heat and a thermal energy storage system's hot gasinjection would supply all other heat, either more or less than half thetotal heat required by the process. The gas flow from the thermal energystorage system at a first temperature would be raised to a higher secondtemperature by such combustion.

In another implementation, the gas flow from the thermal energy storagesystem at a first temperature would be raised by an electric heater to ahigher second temperature, instead of by combustion. Such an electricalheater may be powered by a turbine generator which is powered by heatfrom a thermal storage unit.

In configurations which burn fossil fuels in the presence of nearly pureoxygen and in which it is desirable to retain a relatively pure CO₂stream, the gas flow from a cooling stage may need to be separated fromthe higher temperature process train in order to avoid mixing ambientair with the pure CO₂ and water vapor stream. The heated ambient coolingair may indirectly exchange heat with the thermal energy storage systeminlet flow of nearly pure CO₂ or be used to preheat water for steamgeneration for use elsewhere in the plant or for power generation.Additionally, oxy-fired combustion results in higher temperatures andlower flue gas flow rates. The gas flow of the modified system may beinsufficient to suspend or lift the raw material in the process. Gasflowing through the thermal energy storage system may inject sufficientgas in the calciner to provide the necessary heat for the reaction toproceed. The flue gas and the thermal storage units' injected air wouldmix and flow up through the process, preheating raw material above thecalciner. Eventually, the water is knocked out of the stream bycondensation (lowering the temperature of the gas stream) and a pure CO₂stream remains. A portion of the CO₂ may be recirculated and heated intothe thermal energy storage system with the rest able to be compressedand transported for use in an industrial application, sequestered, or inenhanced oil recovery (EOR) A schematic of the oxyfuel case is depictedin FIG. 10 .

The same advantage is applied if the fuel-fired burner is burninghydrogen. The resulting combustion products are mostly water vaporalthough, as in the oxyfuel case, less flue gas volume is produced perunit heat provided. In this implementation, the cooling air can beutilized, since there is no capturable carbon dioxide gas, and thethermal energy storage system can supply additional high-temperature airto allow for sufficient gas flows and heat delivery to the raw materialin a conventional calcination process. The thermal energy storage systemwould not need to recirculate nearly pure carbon dioxide in this case.The implementation would resemble the process depicted in FIG. 11 withthe only modification being that the “hydrocarbon” fuel is replaced withhydrogen. After water knockout and particulate/fines removal, a portionof the gas is recirculated back into the thermal energy storage system.

In some implementations, the thermal energy storage system delivers heatat a suitable temperature and replaces all burners in which case the hotgas would be injected at the base of the calciner and be recirculated tothe storage system after calcining, preheating, and drying the rawgibbsite material. In some implementations, an electrically poweredheater may be in the outlet gas stream, so as to lift the outlet gastemperature above the internal thermal storage temperature. In suchcases there is no requirement for CO₂ capture, and the design of coolersand airflow may follow the means conventionally used in the prior art.This is shown in FIG. 13 .

The stream may need some treatment before re-entering the thermal energystorage system (i.e. water removal and particulate removal via filter).This is shown in FIG. 10 . The stream may also interact with the coolingstage of the process in order to preheat the recirculated gas prior toentering the thermal storage unit.

Additionally, any thermal storage-calcination integration describedthroughout this disclosure may also apply to this alumina calcinationprocess. In the description of the clay calcination process, there areminor differences in the process such as the reducing zone for qualitycontrol and temperature differences. However, it should be noted thatany described tie-in spot for the thermal storage along with therespective benefits that each integration provides the plant are sharedamongst all described calcination processes, especially between clay andalumina, due to a shared underlying chemical process of hydroxylation.Additionally, throughout the above invention description, wording suchas preheating cyclones, cooling cyclones, and calciners are examples ofconventional calcination processes, but do not describe the details ofwhat may be found in prior art processes.

For the purposes of the integration, preheating and cooling does nothave to take place in a cyclone, as there are other methods forcompleting this stage. If calcining in a rotary kiln, sometimes there isno clear preheating stage, for “preheating” happens at the end of thekiln furthest from the flame. In rotary kiln cases, material is oftencooled in rotary coolers that operate on the same principle, usingcooler gases to convectively cool the activated material. Hence,preheating can mean any stage in a calcination process where hot gasesconvectively heat raw material closer to the activation reactiontemperature and cooling means any process in a calcination process inwhich cooler gas convectively cools the hot activated material afterexiting the kiln or calciner.

Example Implementations of a Calcination System with an IntegratedThermal Energy Storage System.

FIGS. 8A-8C illustrate three scenarios for the integration of a thermalenergy storage (TES) system with a conventional calcination system. Thescenarios will be described in order of intrusiveness from lessintrusive to more intrusive towards conventional calcination processbased on the amount of retrofit or modification to existing equipment isneeded for the integration. The elements of a calcination system with anintegrated TES systems common to all three of the following scenariosinclude a raw gibbsite feed 801, preheat cyclones 803, a calcinationchamber 804, a cooling cyclone 805, a filter 808, an exhaust stack 809,fuel burner 811, hydrocarbon or hydrogen fuel 812 and a thermal energystorage (TES) system 810. Although only one or two of each component isillustrated, it should be understood that the calcination system maycomprise any number of each component, including a plurality of one ormore components.

Raw gibbsite feed 801 receives raw gibbsite and feeds it to preheatcyclone 802 to start the preheat process before entering calcinationchamber 803. In particular, raw gibbsite feed 801 transports rawgibbsite starting material used in the production of aluminum. Differenttypes of feeders may be used as raw gibbsite feed 801, including beltfeeders, screw feeders, vibrating feeders, apron feeders, or rotaryfeeders.

In accordance with the least intrusive scenario illustrated in FIG. 8A,the TES 810 provides moderate heat to a hydrate drier 802. The rawmaterial is fed as a material stream to hydrate drier 802 which isconfigured to remove moisture and dry the raw material from a firstmoisture content to a second, lower moisture content. More specifically,hydrate drier 802 receives heated fluid from the thermal energy storagesystem 810, heats the material stream to evaporate extra moisture, andthe material stream including the dried raw material is fed from thehydrate drier 802 to the preheat cyclone 803. This scenario isconsidered less intrusive because a drier and a TES system can beretrofit into an existing calcination process without necessitatingmajor modifications to existing equipment. Thermal energy storage system810 provides heat to hydrate drier 802 such that the heat transfer fluid(air or steam) indirectly heats the wet hydrate (gibbsite). This lendsto greater energy efficiency, as thermal energy storage (TES) system 810heat transfer fluid, after drying, is recirculated back to the TES forreheating instead of being exhausted to ambient at an elevatedtemperature.

This also enables greater operational flexibility for the facility asthe calciner's operating conditions are detached from the feed hydrate'smoisture content without needing to burn additional fuel. Every 1 wt-%reduction in hydrate moisture content reduces the specific fuelconsumption by 20-30 kJ/kg. Additionally, increasing the hydratetemperature further reduces the specific fuel consumption byapproximately 1 kJ/kg for every 1° C. of increased temperature.

Preheat cyclones 803 receives dried raw gibbsite from hydrate drier 802preheat the dried raw material to a temperature between 800 and 1000° C.before it enters calcination chamber 1-4. Preheat cyclones 803 work byusing a cyclonic action to circulate hot gases around the raw material.Preheat cyclones 803 also help to reduce the amount of fuel required toheat the raw material with the waste heat from combustion chamber 804.Once the dried raw gibbsite is heated to the desired temperature, thematerial enters calcination chamber 804.

Calcination chamber 804 receives heated raw gibbsite from preheatcyclones 803 to provide a controlled environment for the calcinationprocess, which involves heating the gibbsite to a high temperature inthe absence or presence of air. The dried raw product from the preheatcyclones 803 is heated by the combustion of hydrocarbon or hydrogen fuel812 in fuel burner 811. Calcination chamber 804 is designed to maintaina specific temperature range and atmosphere to ensure that the materialbeing processed is heated uniformly and without contamination.Calcination chamber 804 may be lined with heat-resistant materials toprevent damage to the chamber walls, and may be equipped with gas inletsand outlets to allow for the regulation of gas flow and the removal ofbyproducts generated during the calcination process.

Thermal energy storage system 810 provides heat to hydrate drier 802such that the heat transfer fluid (air or steam) indirectly heats thewet hydrate (gibbsite). This lends to greater energy efficiency, asthermal energy storage system 810 heat transfer fluid, after drying, isrecirculated for reheating instead of being exhausted at an elevatedtemperature.

This also enables greater operational flexibility for the facility asthe calciner's operating conditions are detached from the feed hydrate'smoisture content without needing to burn additional fuel. Every 1 wt-%reduction in hydrate moisture content reduces the specific fuelconsumption by 20-30 kJ/kg. Additionally, increasing the hydratetemperature further reduces the specific fuel consumption byapproximately 1 kJ/kg for every 1° C. of increased temperature.

Cooling cyclones 805 receive the product from calcination chamber 804 toreduce the cool down through the intake of ambient air 806. The heatedmaterial from calcination chamber 804 is fed into the top of thecyclone, and as it spirals down through cooling cyclones 805, it iscooled by the flow ambient air 806 that is drawn in through the bottomof cooling cyclones 805. The cool air absorbs the heat from the hotmaterial, and the material is gradually cooled down to a safe handlingtemperature through activated product 807 output.

Filter 808 receives exhaust gases from preheat cyclones 803 to removeparticulate matter from exhaust gases before they are released into theatmosphere through exhaust stack 809. Filter 808 works by using a seriesof fabric bags to capture and remove particulate matter from the exhaustgases. The bags may be made from a woven fabric that is designed toallow air to pass through while trapping particles. As the exhaust gasespass through the bags, the particles become trapped in the fabric. Thegas stream output of the calcination chamber 804 may be provided to thepreheater cyclones 803, filter 808 and exhaust stack 809. The reducedproduct is provided to cooling cyclones 805, where ambient air 806 isprovided for cooling, and may also be provided as an input to thethermal energy storage system 810 (see e.g., FIGS. 8B and 8C). Anactivated material, such as alumina, is provided at activated product807.

In accordance with the scenarios illustrated in FIGS. 8B and 8C, thehydrate drier is eliminated, and high temperature heat generated by theTES 810 is provided directly to the calcination chamber 804.Intermittent electric charging of the thermal energy storage system 810allows energy from renewables such as wind and solar to be used inproviding continuous heat to calcination chamber 804 in a way that doesnot require a drastically different plant process. Optionally and/oradditionally, fuel burner 811 provides a second portion of the heat,which is fueled by hydrocarbon/H₂ fuel 812. The TES 810 may receive astream of ambient air 806. The gas stream may require some treatmentbefore re-entering thermal energy storage system 810 (i.e., waterremoval and particulate removal via filter). The gas stream may alsointeract with the cooling stage of the process cooling cyclones 805 inorder to preheat the recirculated gas prior to entering thermal energystorage system 810, as shown and discussed with respect to FIGS. 11 and12 below. In accordance with the third scenario illustrated in FIG. 8C,the TES 810 receives additional input gas from the exhaust stack 809.

Calcination System Including Integrated Fuel-Fired and Renewable Heatand Power from Thermal Energy Storage System

FIG. 9 illustrates an integrated fuel-fired and TES system for providingheat to power a calcination system with the TES system providing a firstportion of the process heat and the fuel burner providing a secondportion. The calcination system comprises a raw gibbsite feed 901, apreheat cyclones 902, a calcination chamber 903, a cooling cyclone 904,a fuel burner 907, a filter B.2-9, an exhaust stack 910, a thermalenergy storage system 911, and an optional heat exchanger 912. Thesecomponents may be similar or identical to those that have already beendescribed in FIG. B.1 , and therefore, will not be described herein.

In one implementation, the raw material is provided at raw gibbsite feed901. The raw material is fed to preheat cyclones 902. At calcinationchamber 903, the product that is fed through preheat cyclones 902 andheated with non-combustive fuel at calcination chamber 903. Calcinationchamber 903 is heated with non-combustive fluid provided from thermalstorage unit 9011, which is provided by renewable energy from thermalenergy storage system 911. Additionally, fuel burner 907 provides asecond portion of the heat, which is fueled by hydrocarbon/H₂ fuel 908.The gas stream may also be provided to preheater cyclone 902, filter 909and exhaust stack 910. Optional heat exchanger 912 may be incorporatedto transfer heat from preheat cyclones 902 to the filter 909, and toheat the input fluid to the thermal energy storage system 911. Thereduced product is provided to cooling cyclones 904, where ambient air905 is provided for cooling. Ambient air 905 may also be circulated intothermal energy storage system 911. Activated material includes materialwhich has been dehydroxylated, such as alumina. Activated material isprovided as a product at activated product 906.

Thermal energy storage system 911 can supply heat and integrate to thealumina calcination process in a means similar to its integration into aclay calcination process described in greater detail above. Combustionin fuel burners 907 may be reduced or eliminated with the majority orall the heat input to the system coming from the thermal energy storagesystem 911. Hot fluid (e.g., hot gas) that has been heated by thethermal energy storage system 911 may be injected to contact andinteract with the raw material coming from the raw gibbsite feed 901 andpassing though preheat cyclones 902. This gas may be air or anotherworking fluid such as CO₂ or a mixture in any proportion of gasesincluding air, oxygen, and CO₂.

One implementation has the thermal energy storage system 911 providing afirst portion of the process heat, and a fuel burner 907 providing asecond portion. Fuel burner 907 receives hydrocarbon/H₂ fuel 908 toreduce the fuel consumption of fuel burner 907. The fuel is mixed withair or oxygen and ignited to produce a flame, which provides the heatenergy required for calcination. In this example, the thermal energystorage system 911 reduces the fuel consumption of fuel burner 907, anda portion of the exhaust gas that is normally released to theenvironment after particulate filtering is recirculated back into thethermal energy storage system 911 for reheating. The gas being passedthrough thermal energy storage system 911 may also include ambient air905 from the environment in order to control temperature and modulatethe gas mixtures chemical composition.

Calcination System Including Integrated Oxyfuel-Fired and Renewable Heatand Power from Thermal Energy Storage System

FIG. 10 illustrates an integrated oxyfuel-fired and renewable heat andpower system powering a calcination system with the thermal energystorage system according to an example implementation. The calcinationsystem comprises a raw gibbsite feed 1001, an optional hydrate drier1002, a preheat cyclone 1003, a calcination chamber 1004, a coolingcyclone 1005, a fuel burner 1008, an optional air separation unit 1010,a filter with water knockout 1011, a CO₂ export 1012, a thermal energystorage system 1013, and indirect gas-gas heat exchanger 1014 thatreceives the output heated fluid of the cooling cyclones 1005 and theheated fluid output from the filter 1011, and an optional heat exchanger10016. These components may be similar or identical to those that havealready been described in FIGS. 8-9 and therefore, will not be describedherein.

In one implementation, the raw material is provided at raw gibbsite feed1001. The system may include an optional hydrate drier 1002 to removemoisture from raw material. The raw material is fed to preheat cyclones1003. At calcination chamber 1004, the product that is fed through thecyclones and heated with non-combustive fuel at the calcination chamber1004. Calcination chamber 1004 is heated with non-combustive fluidprovided from thermal storage unit 1013, which is provided by renewableenergy from thermal energy storage system, 1013. Additionally, a fuelburner 1008 can be fed oxygen by optional air separator unit 1010 toprovide a second portion of the heat through oxyfuel combustion. Byburning with oxygen instead of air, the result is cleaner burning at ahigher temperature, with no NOx related byproducts as would be producedwith air as an input for the fuel burner 3-8.

The gas stream may also be provided to preheater cyclones 1003, filterand knockout 1011 and an indirect gas-gas heat exchanger 1014. Thereduced product from calcination chamber 1004 is provided to coolingcyclones 1004, where ambient air 1006 is provided for cooling, eitherdirectly or indirectly via the cooling cyclones 1005. An activatedmaterial, such as activated alumina is provided as an output atactivated product 1007. Additionally, oxy-fired combustion results inhigher temperatures and lower flue gas flow rates. The gas flow of themodified system may be insufficient to suspend or lift the raw materialfrom the raw gibbsite feed 1001 in the process. Thermal energy storagesystem 1013 injects sufficient gas into calciner chamber 1004 to providethe necessary heat for the reaction to proceed. The flue gas and theinjected air from thermal energy storage system 1013 mix and flow upthrough the process preheating raw material above calciner chamber 1004.Eventually, the water is knocked out of the stream by condensation(lowering the temperature of the gas stream) through filter and waterknockout 1011 and a pure CO₂ stream that remains is exhausted throughCO₂ export 1012. A portion of the CO₂ is recirculated into thermalenergy storage system 10013, with the rest of the CO₂ configured tocompressed and transported for use in an industrial application,sequestered, or used in EOR. In accordance with another implementation,an optional heat exchanger (not shown) may be provided to produce steamusing the heat from the exhaust gas exiting the calcination chamber1004. The produced steam may be used as input steam to drive a turbine(not shown) to generate electricity.

In configurations which burn fossil fuel and in which it is desirable toretain a relatively pure CO₂ stream, the gas flow from a cooling stageat cooling cyclones 1004 may need to be separated from the highertemperature process train in order to avoid mixing ambient air with thepure CO₂ and water vapor stream. The heated ambient cooling air mayindirectly exchange heat with thermal energy storage system 10013 inletflow of nearly pure CO₂ or be used to preheat water for steam generationfor use elsewhere in the plant or for power generation.

Calcination System Including Renewable Heat and Power from ThermalEnergy Storage System with Electric Booster

FIG. 11 illustrates a calcination system with an integrated TES systemwith optional electric booster for providing high temperature gas to thecalciner to increase the bulk temperature of the incoming gas streams(primary/secondary air within the reactor. The calcination systemcomprises a raw gibbsite feed 1101, a hydrate a preheat cyclones 1102, acalcination chamber 1103, a cooling cyclone 1104, a filter 1107, anexhaust stack 1108, a thermal energy storage system 1109, and anoptional electric booster 1110. Although only one or two of eachcomponent is illustrated, it should be understood that the calcinationsystem may comprise any number of each component, including a pluralityof one or more components. These components may be similar or identicalto those that have already been described in FIG. B.1 , and therefore,will not be described herein.

FIG. 11 shows the input to the TES 1109 as ambient air 1106. Althoughnot shown in the example implementation in FIG. 11 , it is understoodthat the TES 810 may also receive additional inputs of air and gas fromone or more additional sources in the calcination process including butnot limited to the output air from exhaust stack 809 and the output gasfrom the cooling cyclones 805. The output gas from the cooling cyclones805 can be fed as a direct input to the TES 810. Optionally, if theoutput gas stream from the cooling cyclones 1104 is too dirty, it can bepassed through an indirect gas-gas heat exchanger similar to theconfiguration shown by reference number 1014 in FIG. 10 .

In some implementations, thermal energy storage system 1109 deliversheat at a suitable temperature and replaces all burners in which casethe hot gas would be injected at the base of calciner chamber 1103 andbe recirculated to thermal energy storage system 1109 after calcining,preheating, and drying the raw gibbsite material from raw gibbsite feed1101. The temperature of the heated fluid coming from thermal energystorage system 1109 may be further lifted/increased via optionalelectric booster 1110. In some implementations, an electrically poweredheater may be in the outlet gas stream to lift the outlet gastemperature above the internal thermal storage temperature. In suchcases there is no requirement for CO₂ capture, and the design of coolersand airflow may follow the means conventionally used in the prior art.Modifications to the calciner may be required as heat transfer kineticsare reduced when radiant fuel-firing is replaced by the TES system. Insome implementations, the heat provided to the calciner by the TESsystem is superheated steam. The improved heat transfer characteristicsof steam compared to air may make the integration of the TES lessintrusive and this provides opportunity for improved heat recovery suchas preheating the boiler feedwater from cooling water in a fluidized bedcooler or water vapor knockout from the waste gas stream.

To the extent a term used in a claim is not defined below, it should begiven the broadest definition persons in the pertinent art have giventhat term as reflected in printed publications and issued patents at thetime of filing. For example, the following terminology may be usedinterchangeably, as would be understood to those skilled in the art:

-   -   A Amperes    -   AC Alternating current    -   DC Direct current    -   DFB Dual Fluidized Bed    -   EOR Enhanced Oil Recovery    -   EV Electric vehicle    -   GT Gas turbine    -   HRSG Heat recovery steam generator    -   kV kilovolt    -   kW kilowatt    -   MED Multi-effect desalination    -   MPPT Maximum power point tracking    -   MSF Multi-stage flash    -   MW megawatt    -   OTSG Once-through steam generator    -   PEM Proton-exchange membrane    -   PV Photovoltaic    -   RSOC Reversible solid oxide cell    -   SOEC Solid oxide electrolyzer cell    -   SOFC Solid oxide fuel cell    -   ST Steam turbine    -   TES Thermal Energy Storage    -   TSU Thermal Storage Unit

Additionally, the term “heater” is used to refer to a conductive elementthat generates heat. For example, the term “heater” as used in thepresent example implementations may include, but is not limited to, awire, a ribbon, a tape, or other structure that can conduct electricityin a manner that generates heat. The composition of the heater may bemetallic (coated or uncoated), ceramic or other composition that cangenerate heat.

While foregoing example implementations may refer to “air”, includingCO₂, the inventive concept is not limited to this composition, and otherfluid streams may be substituted therefor for additional industrialapplications. For example, but by way of limitation, enhanced oilrecovery, sterilization related to healthcare or food and beverages,drying, chemical production, desalination and hydrothermal processing(e.g. Bayer process.) The Bayer process includes a calcination step. Thecomposition of fluid streams may be selected to improve product yieldsor efficiency, or to control the exhaust stream.

In any of the thermal storage units, the working fluid composition maybe changed at times for a number of purposes, including maintenance orre-conditioning of materials. Multiple units may be used in synergy toimprove charging or discharging characteristics, sizing or ease ofinstallation, integration or maintenance. As would be understood bythose skilled in the art, the thermal storage units disclosed herein maybe substituted with other thermal storage units having the necessaryproperties and functions; results may vary, depending on the manner andscale of combination of the thermal storage units.

As used in the description herein and throughout the claims that follow,the meaning of “a,” “an,” and “the” includes plural reference unless thecontext clearly dictates otherwise. Also, as used in the descriptionherein, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise.

The recitation of ranges of values herein is merely intended to serve asa shorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided with respect to certain example implementationsherein is intended merely to better illuminate the exampleimplementation and does not pose a limitation on the scope of theexample implementation otherwise claimed. No language in thespecification should be construed as indicating any non-claimed elementessential to the practice of the example implementation.

Groupings of alternative elements or example implementations of theexample implementation disclosed herein are not to be construed aslimitations. Each group member can be referred to and claimedindividually or in any combination with other members of the group orother elements found herein. One or more members of a group can beincluded in, or deleted from, a group for reasons of convenience and/orpatentability. When any such inclusion or deletion occurs, thespecification is herein deemed to contain the group as modified thusfulfilling the written description of all groups used in the appendedclaims.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, devices, etc. described herein may be positioned in any desiredorientation. Thus, the use of terms such as “above,” “below,” “upper,”“lower,” “first”, “second” or other like terms to describe a spatialrelationship between various components or to describe the spatialorientation of aspects of such components should be understood todescribe a relative relationship between the components or a spatialorientation of aspects of such components, respectively, as the devicedescribed herein may be oriented in any desired direction.

In interpreting the specification, all terms should be interpreted inthe broadest possible manner consistent with the context. In particular,the terms “comprises” and “comprising” should be interpreted asreferring to elements, components, or steps in a non-exclusive manner,indicating that the referenced elements, components, or steps may bepresent, or utilized, or combined with other elements, components, orsteps that are not expressly referenced. Where the specification claimsrefer to at least one of something selected from the group consisting ofA, B, C . . . and N, the text should be interpreted as requiring onlyone element from the group, not A plus N, or B plus N, etc.

While the foregoing describes various example implementations of theexample implementation, other and further example implementations of theexample implementation may be devised without departing from the basicscope thereof. The scope of the example implementation is determined bythe claims that follow. The example implementation is not limited to thedescribed example implementations, versions or examples, which areincluded to enable a person having ordinary skill in the art to make anduse the example implementation when combined with information andknowledge available to the person having ordinary skill in the art.

1. A calcination system, including: a thermal energy storage (TES)system configured to store thermal energy derived from a variablerenewable energy source having intermittent availability, wherein theTES system is configured to heat a storage medium using electricity fromthe renewable energy source, and deliver heat to a use in the form of aheated fluid; and a calciner configured to receive and heat a materialstream with thermal energy provided by a heated fluid source andgenerate a calcined product; and wherein at least a first portion of theheated fluid source is provided by the TES system.
 2. The calcinationsystem of claim 1 further including: a hydrate drier configured toevaporate moisture from the material stream having a first moisturecontent to a second, lower moisture content by transferring thermalenergy from the heated fluid provided by the TES system into thematerial stream prior to entering the calciner so that less thermalenergy is required by the calciner to generate the calcined product. 3.The calcination system of claim 1, wherein a second portion of theheated fluid source is provided by a fuel burner that is configured toburn hydrogen or hydrocarbon fuel.
 4. The calcination system of claim 3,wherein the fuel burner is configured to operate with combustion airhaving a higher oxygen composition by volume than in ambient air.
 5. Thecalcination system of claim 1, wherein the calciner is furtherconfigured to remove impurities or volatile substances from the materialstream and/or to incur thermal decomposition to the calcined product. 6.The calcination system of claim 1, wherein the fluid is a non-combustivefluid.
 7. The calcination system of claim 5, wherein the non-combustivefluid comprises carbon dioxide, air, a mixture of gases, or steam. 8.The calcination system of claim 1, wherein the material stream input tothe calciner includes aluminum hydroxide, and the calcined productgenerated by the calciner principally comprises alumina.
 9. Thecalcination system of claim 1, further including: a preheat cycloneconfigured to heat the dried material from the hydrate drier prior toentering the calciner; a cooling cyclone configured to cool heatedproduct received from the calciner using a source of ambient air; andwherein exhaust fluid output from one or both of the preheat cyclone andcooling cyclone is circulated back to the TES system as the fluid to beheated by the TES system.
 10. The calcination system of claim 7, furtherincluding a heat exchanger configured to receive thermal energy obtainedfrom the exhaust fluid from one or both of the preheat cyclone andcooling cyclone, and to apply the thermal energy from the exhaust fluidto heat the fluid that is input to the TES system.
 11. The calcinationsystem of claim 1, further including an electric booster configured toraise temperature of the heated fluid delivered by the TES from a firsttemperature to a second higher temperature.
 12. The calcination systemof claim 11, wherein the electric booster is powered by a turbinegenerator.
 13. The calcination system of claim 12, wherein the turbineis powered at least partially by heat from the TES system.
 14. Thecalcination system of claim 1, wherein the heated fluid provided fromthe TES system to the calciner generates steam for use in steam partialcalcination.
 15. A calcination system, including: a thermal energystorage (TES) system configured to store thermal energy derived from avariable renewable energy source having intermittent availability,wherein the TES system is configured to deliver heat to a use in theform of a heated fluid; a calciner configured to receive and heat amaterial stream with thermal energy provided by a heated fluid sourceand generate an calcined product; and wherein the heated fluid sourceincludes a primary fuel burner configured to provide a first portion ofthe thermal energy required by the calciner to generate the calcinedproduct and wherein the TES system provides a second portion of thethermal energy required by the calciner to generate the calcinedproduct.
 16. The calcination system of claim 15, wherein the secondportion of the thermal energy provided by the TES system is heatedfluid.
 17. The calcination system of claim 15, wherein the TES systemprovides the heated fluid to the calciner as direct heated fluid. 18.The calcination system of claim 15, wherein the TES system provides theheated fluid to generate steam for use in steam partial calcination. 19.The calcination system of claim 15, wherein the primary fuel burner isconfigured to operate with combustion air having a higher oxygencomposition by volume than in ambient air.
 20. The calcination system ofclaim 19, wherein the second portion of thermal energy is provided toburner inputs of the primary fuel burner to increase flame temperatureso that the calciner receives higher temperature heat.
 21. Thecalcination system of claim 15, wherein the primary fuel burner isconfigured to burn a fuel source that includes greater than 0.5%molecular hydrogen.
 21. (canceled)
 22. The calcination system of claim15, further including: a heat exchanger configured to produce steam fromexhaust gas exiting the calciner; and a turbine configured to generateelectricity using the produced steam.
 23. A method of calcination,including: storing thermal energy derived from a variable renewableenergy source having intermittent availability by a thermal energystorage (TES) system, by heating a storage medium using electricity fromthe variable renewable energy source, and delivering useful heat in theform of a heated fluid; in a calciner, receiving and heating thematerial stream with the heated fluid delivered by the TES system, so asto calcine the material stream, and generate an calcined product. 24.The method of claim 23, wherein the applying the received thermal energyincludes: injecting the material stream via a first inlet of thecalciner; and injecting, via a second inlet of the calciner, the heatedfluid from the TES system so as to suspend the injected material streamwithin the calciner.
 25. The method of claim 23, further including:prior to being received by the calciner, pre-heating the material streamby transferring thermal energy from the heated fluid into the materialstream; and at the calciner, receiving the pre-heated material streamand applying the received thermal energy to further heat the materialstream to a higher temperature than the pre-heated material stream. 26.The method of claim 23, wherein carbon dioxide gas is circulated fromthe calciner to the TES system as fluid to be heated by the TES system.27. The method of claim 23, further including receiving thermal energyobtained from exhaust gas exiting the calciner and applying the receivedthermal energy from the exhaust gas to heat fluid that is input to theTES system.
 28. The method of claim 23, wherein the fluid is anon-combustive fluid.
 29. The method of claim 28, wherein thenon-combustive fluid includes carbon dioxide, air, or a mixture ofgases.
 30. The method of claim 23, wherein the material stream input tothe calciner includes aluminum hydroxide in mineral form, and thecalcined product generated by the calciner comprises alumina.
 31. Themethod of claim 23, further including a fuel burner configured toprovide the calciner with a source of heat, wherein a fuel input to thefuel burner is at least one of oxyfuel and hydrogen.
 32. The method ofclaim 23, further including receiving carbon dioxide gas and an outputheated fluid from a cooling cyclone that cools the calcined productgenerated by the calciner, and transferring the heat to a fluid streamthat is provided as an input to the TES system.
 33. The method of claim23, further including an electric booster positioned between the TESsystem and the calciner and configured to raise the temperature of thefluid output by the TES system to a higher temperature.
 34. The methodof claim 23, wherein the electric booster is powered by a turbinegenerator.
 35. The method of claim 34, wherein the turbine generator ispowered by heat from the TES system.
 36. The method of claim 23, whereinthe heated fluid is provided from the TES system to the calciner asdirect heated fluid.
 37. The method of claim 23, wherein the heatedfluid is provided from the TES system to the calciner to generate steamfor use in steam partial calcination.
 38. The calcination system ofclaim 15, wherein a portion of exhaust gas from the calciner isrecirculated back into the TES for reheating.